Historically we didn't call VCPUOP_register_vcpu_info for CPU0 for
PVHVM guests (while we had it for PV and ARM guests). This is usually
fine as we can use vcpu info in the shared_info page but when we try
booting on a vCPU with Xen's vCPU id > 31 (e.g. when we try to kdump
after crashing on this CPU) we're not able to boot.

Switch to always doing VCPUOP_register_vcpu_info for the boot CPU.
Signed-off-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

HYPERVISOR_vcpu_op() passes Linux's idea of vCPU id as a parameter
while Xen's idea is expected. In some cases these ideas diverge so we
need to do remapping.

Convert all callers of HYPERVISOR_vcpu_op() to use xen_vcpu_nr().

Leave xen_fill_possible_map() and xen_filter_cpu_maps() intact as
they're only being called by PV guests before perpu areas are
initialized. While the issue could be solved by switching to
early_percpu for xen_vcpu_id I think it's not worth it: PV guests will
probably never get to the point where their idea of vCPU id diverges
from Xen's.
Signed-off-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

This call has always been missing from xen_play dead() but until
recently this was rather benign. With new cpu hotplug framework
(commit 8df3e07e ("cpu/hotplug: Let upcoming cpu bring itself fully up").
however this call is required, otherwise a hot-plugged CPU will not
be properly brough up (by never calling cpuhp_online_idle())
Signed-off-by: NBoris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Let the non boot cpus call into idle with the corresponding hotplug state, so
the hotplug core can handle the further bringup. That's a first step to
convert the boot side of the hotplugged cpus to do all the synchronization
with the other side through the state machine. For now it'll only start the
hotplug thread and kick the full bringup of the cpu.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.614102639@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

Based on include/xen/mm.h [1], Linux is mistakenly using MFN when GFN
is meant, I suspect this is because the first support for Xen was for
PV. This resulted in some misimplementation of helpers on ARM and
confused developers about the expected behavior.

For instance, with pfn_to_mfn, we expect to get an MFN based on the name.
Although, if we look at the implementation on x86, it's returning a GFN.

For clarity and avoid new confusion, replace any reference to mfn with
gfn in any helpers used by PV drivers. The x86 code will still keep some
reference of pfn_to_mfn which may be used by all kind of guests
No changes as been made in the hypercall field, even
though they may be invalid, in order to keep the same as the defintion
in xen repo.

Note that page_to_mfn has been renamed to xen_page_to_gfn to avoid a
name to close to the KVM function gfn_to_page.

Take also the opportunity to simplify simple construction such
as pfn_to_mfn(page_to_pfn(page)) into xen_page_to_gfn. More complex clean up
will come in follow-up patches.

[1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=e758ed14f390342513405dd766e874934573e6cbSigned-off-by: NJulien Grall <julien.grall@citrix.com>
Reviewed-by: NStefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

Map shared data structure that will hold CPU registers, VPMU context,
V/PCPU IDs of the CPU interrupted by PMU interrupt. Hypervisor fills
this information in its handler and passes it to the guest for further
processing.

Set up PMU VIRQ.

Now that perf infrastructure will assume that PMU is available on a PV
guest we need to be careful and make sure that accesses via RDPMC
instruction don't cause fatal traps by the hypervisor. Provide a nop
RDPMC handler.

For the same reason avoid issuing a warning on a write to APIC's LVTPC.

Both of these will be made functional in later patches.
Signed-off-by: NBoris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: NDavid Vrabel <david.vrabel@citrix.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

Some of x86 bare-metal and Xen CPU initialization code is common
between the two and therefore can be factored out to avoid code
duplication.

As a side effect, doing so will also extend the fix provided by
commit a7fcf28d ("x86/asm/entry: Replace this_cpu_sp0() with
current_top_of_stack() to x86_32") to 32-bit Xen PV guests.
Signed-off-by: NBoris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: NDavid Vrabel <david.vrabel@citrix.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: konrad.wilk@oracle.com
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1427897534-5086-1-git-send-email-boris.ostrovsky@oracle.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

PER_CPU_VAR(kernel_stack) was set up in a way where it points
five stack slots below the top of stack.

Presumably, it was done to avoid one "sub $5*8,%rsp"
in syscall/sysenter code paths, where iret frame needs to be
created by hand.

Ironically, none of them benefits from this optimization,
since all of them need to allocate additional data on stack
(struct pt_regs), so they still have to perform subtraction.

This patch eliminates KERNEL_STACK_OFFSET.

PER_CPU_VAR(kernel_stack) now points directly to top of stack.
pt_regs allocations are adjusted to allocate iret frame as well.
Hopefully we can merge it later with 32-bit specific
PER_CPU_VAR(cpu_current_top_of_stack) variable...

Net result in generated code is that constants in several insns
are changed.

This change is necessary for changing struct pt_regs creation
in SYSCALL64 code path from MOV to PUSH instructions.
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
Acked-by: NBorislav Petkov <bp@suse.de>
Acked-by: NAndy Lutomirski <luto@kernel.org>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1426785469-15125-2-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

This commit removes the open-coded CPU-offline notification with new
common code.  Among other things, this change avoids calling scheduler
code using RCU from an offline CPU that RCU is ignoring.  It also allows
Xen to notice at online time that the CPU did not go offline correctly.
Note that Xen has the surviving CPU carry out some cleanup operations,
so if the surviving CPU times out, these cleanup operations might have
been carried out while the outgoing CPU was still running.  It might
therefore be unwise to bring this CPU back online, and this commit
avoids doing so.
Signed-off-by: NBoris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: <x86@kernel.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: <xen-devel@lists.xenproject.org>

Call __set_current_state() instead of assigning the new state directly.
These interfaces also aid CONFIG_DEBUG_ATOMIC_SLEEP environments,
keeping track of who changed the state.
Signed-off-by: NDavidlohr Bueso <dbueso@suse.de>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

Commit 2ed53c0d ("x86/smpboot: Speed up suspend/resume by
avoiding 100ms sleep for CPU offline during S3") introduced
completions to CPU offlining process. These completions are not
initialized on Xen kernels causing a panic in
play_dead_common().

Move handling of die_complete into common routines to make them
available to Xen guests.
Signed-off-by: NBoris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: NDavid Vrabel <david.vrabel@citrix.com>
Cc: tianyu.lan@intel.com
Cc: konrad.wilk@oracle.com
Cc: xen-devel@lists.xenproject.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1414770572-7950-1-git-send-email-boris.ostrovsky@oracle.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

This fixes two bugs in PVH guests:

  - Not setting EFER.NX means the NX bit in page table entries is
    ignored on Intel processors and causes reserved bit page faults on
    AMD processors.

  - After the Xen commit 7645640d6ff1 ("x86/PVH: don't set EFER_SCE for
    pvh guest") PVH guests are required to set EFER.SCE to enable the
    SYSCALL instruction.

Secondary VCPUs are started with pagetables with the NX bit set so
EFER.NX must be set before using any stack or data segment.
xen_pvh_cpu_early_init() is the new secondary VCPU entry point that
sets EFER before jumping to cpu_bringup_and_idle().
Signed-off-by: NMukesh Rathor <mukesh.rathor@oracle.com>
Reviewed-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

Hang is observed on virtual machines during CPU hotplug,
especially in big guests with many CPUs. (It reproducible
more often if host is over-committed).

It happens because master CPU gives up waiting on
secondary CPU and allows it to run wild. As result
AP causes locking or crashing system. For example
as described here:

  https://lkml.org/lkml/2014/3/6/257

If master CPU have sent STARTUP IPI successfully,
and AP signalled to master CPU that it's ready
to start initialization, make master CPU wait
indefinitely till AP is onlined.

To ensure that AP won't ever run wild, make it
wait at early startup till master CPU confirms its
intention to wait for AP. If AP doesn't respond in 10
seconds, the master CPU will timeout and cancel
AP onlining.
Signed-off-by: NIgor Mammedov <imammedo@redhat.com>
Acked-by: NToshi Kani <toshi.kani@hp.com>
Tested-by: NBoris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1403266991-12233-1-git-send-email-imammedo@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Commit 198d208d ("x86: Keep
thread_info on thread stack in x86_32") made 32-bit kernels use
kernel_stack to point to thread_info. That change missed a couple of
updates needed by Xen's 32-bit PV guests:

1. kernel_stack needs to be initialized for secondary CPUs

2. GET_THREAD_INFO() now uses %fs register which may not be the
   kernel's version when executing xen_iret().

With respect to the second issue, we don't need GET_THREAD_INFO()
anymore: we used it as an intermediate step to get to per_cpu xen_vcpu
and avoid referencing %fs. Now that we are going to use %fs anyway we
may as well go directly to xen_vcpu.
Signed-off-by: NBoris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

otherwise we will get for some user-space applications
that use 'clone' with CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID
end up hitting an assert in glibc manifested by:

general protection ip:7f80720d364c sp:7fff98fd8a80 error:0 in
libc-2.13.so[7f807209e000+180000]

This is due to the nature of said operations which sets and clears
the PID.  "In the successful one I can see that the page table of
the parent process has been updated successfully to use a
different physical page, so the write of the tid on
that page only affects the child...

On the other hand, in the failed case, the write seems to happen before
the copy of the original page is done, so both the parent and the child
end up with the same value (because the parent copies the page after
the write of the child tid has already happened)."
(Roger's analysis). The nature of this is due to the Xen's commit
of 51e2cac257ec8b4080d89f0855c498cbbd76a5e5
"x86/pvh: set only minimal cr0 and cr4 flags in order to use paging"
the CR0_WP was removed so COW features of the Linux kernel were not
operating properly.

While doing that also update the rest of the CR0 flags to be inline
with what a baremetal Linux kernel would set them to.

In 'secondary_startup_64' (baremetal Linux) sets:

X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | X86_CR0_NE | X86_CR0_WP |
X86_CR0_AM | X86_CR0_PG

The hypervisor for HVM type guests (which PVH is a bit) sets:
X86_CR0_PE | X86_CR0_ET | X86_CR0_TS
For PVH it specifically sets:
X86_CR0_PG

Which means we need to set the rest: X86_CR0_MP | X86_CR0_NE  |
X86_CR0_WP | X86_CR0_AM to have full parity.
Signed-off-by: NRoger Pau Monne <roger.pau@citrix.com>
Signed-off-by: NMukesh Rathor <mukesh.rathor@oracle.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
[v1: Took out the cr4 writes to be a seperate patch]
[v2: 0-DAY kernel found xen_setup_gdt to be missing a static]

The VCPU bringup protocol follows the PV with certain twists.
From xen/include/public/arch-x86/xen.h:

Also note that when calling DOMCTL_setvcpucontext and VCPU_initialise
for HVM and PVH guests, not all information in this structure is updated:

 - For HVM guests, the structures read include: fpu_ctxt (if
 VGCT_I387_VALID is set), flags, user_regs, debugreg[*]

 - PVH guests are the same as HVM guests, but additionally use ctrlreg[3] to
 set cr3. All other fields not used should be set to 0.

This is what we do. We piggyback on the 'xen_setup_gdt' - but modify
a bit - we need to call 'load_percpu_segment' so that 'switch_to_new_gdt'
can load per-cpu data-structures. It has no effect on the VCPU0.

We also piggyback on the %rdi register to pass in the CPU number - so
that when we bootup a new CPU, the cpu_bringup_and_idle will have
passed as the first parameter the CPU number (via %rdi for 64-bit).
Signed-off-by: NMukesh Rathor <mukesh.rathor@oracle.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

This patch proposes to remove the IRQF_DISABLED flag from x86/xen
code. It's a NOOP since 2.6.35 and it will be removed one day.
Signed-off-by: NMichael Opdenacker <michael.opdenacker@free-electrons.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Due to the way kernel is initialized under Xen is possible that the
ring1 selector used by the kernel for the boot cpu end up to be copied
to userspace leading to segmentation fault in the userspace.

Xen code in the kernel initialize no-boot cpus with correct selectors (ds
and es set to __USER_DS) but the boot one keep the ring1 (passed by Xen).
On task context switch (switch_to) we assume that ds, es and cs already
point to __USER_DS and __KERNEL_CSso these selector are not changed.

If processor is an Intel that support sysenter instruction sysenter/sysexit
is used so ds and es are not restored switching back from kernel to
userspace. In the case the selectors point to a ring1 instead of __USER_DS
the userspace code will crash on first memory access attempt (to be
precise Xen on the emulated iret used to do sysexit will detect and set ds
and es to zero which lead to GPF anyway).

Now if an userspace process call kernel using sysenter and get rescheduled
(for me it happen on a specific init calling wait4) could happen that the
ring1 selector is set to ds and es.

This is quite hard to detect cause after a while these selectors are fixed
(__USER_DS seems sticky).

Bisecting the code commit 7076aada appears
to be the first one that have this issue.
Signed-off-by: NFrediano Ziglio <frediano.ziglio@citrix.com>
Signed-off-by: NStefano Stabellini <stefano.stabellini@eu.citrix.com>
Reviewed-by: NAndrew Cooper <andrew.cooper3@citrix.com>

Before this patch we would patch all of the pv_lock_ops sites
using alternative assembler. Then later in the bootup cycle
change the unlock_kick and lock_spinning to the Xen specific -
without re patching.

That meant that for the core of the kernel we would be running
with the baremetal version of unlock_kick and lock_spinning while
for modules we would have the proper Xen specific slowpaths.

As most of the module uses some API from the core kernel that ended
up with slowpath lockers waiting forever to be kicked (b/c they
would be using the Xen specific slowpath logic). And the
kick never came b/c the unlock path that was taken was the
baremetal one.

On PV we do not have the problem as we initialise before the
alternative code kicks in.

The fix is to make the updating of the pv_lock_ops function
be done before the alternative code starts patching.

Note that this patch fixes issues discovered by commit
f10cd522.
("xen: disable PV spinlocks on HVM") wherein it mentioned

   PV spinlocks cannot possibly work with the current code because they are
   enabled after pvops patching has already been done, and because PV
   spinlocks use a different data structure than native spinlocks so we
   cannot switch between them dynamically.

The first problem is solved by this patch.

The second problem has been solved by commit
816434ec
(Merge branch 'x86-spinlocks-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip)

P.S.
There is still the commit 70dd4998
(xen/spinlock: Disable IRQ spinlock (PV) allocation on PVHVM) to
revert but that can be done later after all other bugs have been
fixed.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: NDavid Vrabel <david.vrabel@citrix.com>

The xen_lock_spinning has a check for the kicker interrupts
and if it is not initialized it will spin normally (not enter
the slowpath).

But for PVHVM case we would initialize the kicker interrupt
before the CPU came online. This meant that if the booting
CPU used a spinlock and went in the slowpath - it would
enter the slowpath and block forever. The forever part because
during bootup: the spinlock would be taken _before_ the CPU
sets itself to be online (more on this further), and we enter
to poll on the event channel forever.

The bootup CPU (see commit fc78d343
"xen/smp: initialize IPI vectors before marking CPU online"
for details) and the CPU that started the bootup consult
the cpu_online_mask to determine whether the booting CPU should
get an IPI. The booting CPU has to set itself in this mask via:

  set_cpu_online(smp_processor_id(), true);

However, if the spinlock is taken before this (and it is) and
it polls on an event channel - it will never be woken up as
the kernel will never send an IPI to an offline CPU.

Note that the PVHVM logic in sending IPIs is using the HVM
path which has numerous checks using the cpu_online_mask
and cpu_active_mask. See above mention git commit for details.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: NDavid Vrabel <david.vrabel@citrix.com>

An older PVHVM guest (v3.0 based) crashed during vCPU hot-plug with:

	kernel BUG at drivers/xen/events.c:1328!

RCU has detected that a CPU has not entered a quiescent state within the
grace period.  It needs to send the CPU a reschedule IPI if it is not
offline.  rcu_implicit_offline_qs() does this check:

	/*
	 * If the CPU is offline, it is in a quiescent state.  We can
	 * trust its state not to change because interrupts are disabled.
	 */
	if (cpu_is_offline(rdp->cpu)) {
		rdp->offline_fqs++;
		return 1;
	}

	Else the CPU is online.  Send it a reschedule IPI.

The CPU is in the middle of being hot-plugged and has been marked online
(!cpu_is_offline()).  See start_secondary():

	set_cpu_online(smp_processor_id(), true);
	...
	per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;

start_secondary() then waits for the CPU bringing up the hot-plugged CPU to
mark it as active:

	/*
	 * Wait until the cpu which brought this one up marked it
	 * online before enabling interrupts. If we don't do that then
	 * we can end up waking up the softirq thread before this cpu
	 * reached the active state, which makes the scheduler unhappy
	 * and schedule the softirq thread on the wrong cpu. This is
	 * only observable with forced threaded interrupts, but in
	 * theory it could also happen w/o them. It's just way harder
	 * to achieve.
	 */
	while (!cpumask_test_cpu(smp_processor_id(), cpu_active_mask))
		cpu_relax();

	/* enable local interrupts */
	local_irq_enable();

The CPU being hot-plugged will be marked active after it has been fully
initialized by the CPU managing the hot-plug.  In the Xen PVHVM case
xen_smp_intr_init() is called to set up the hot-plugged vCPU's
XEN_RESCHEDULE_VECTOR.

The hot-plugging CPU is marked online, not marked active and does not have
its IPI vectors set up.  rcu_implicit_offline_qs() sees the hot-plugging
cpu is !cpu_is_offline() and tries to send it a reschedule IPI:
This will lead to:

	kernel BUG at drivers/xen/events.c:1328!

	xen_send_IPI_one()
	xen_smp_send_reschedule()
	rcu_implicit_offline_qs()
	rcu_implicit_dynticks_qs()
	force_qs_rnp()
	force_quiescent_state()
	__rcu_process_callbacks()
	rcu_process_callbacks()
	__do_softirq()
	call_softirq()
	do_softirq()
	irq_exit()
	xen_evtchn_do_upcall()

because xen_send_IPI_one() will attempt to use an uninitialized IRQ for
the XEN_RESCHEDULE_VECTOR.

There is at least one other place that has caused the same crash:

	xen_smp_send_reschedule()
	wake_up_idle_cpu()
	add_timer_on()
	clocksource_watchdog()
	call_timer_fn()
	run_timer_softirq()
	__do_softirq()
	call_softirq()
	do_softirq()
	irq_exit()
	xen_evtchn_do_upcall()
	xen_hvm_callback_vector()

clocksource_watchdog() uses cpu_online_mask to pick the next CPU to handle
a watchdog timer:

	/*
	 * Cycle through CPUs to check if the CPUs stay synchronized
	 * to each other.
	 */
	next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
	if (next_cpu >= nr_cpu_ids)
		next_cpu = cpumask_first(cpu_online_mask);
	watchdog_timer.expires += WATCHDOG_INTERVAL;
	add_timer_on(&watchdog_timer, next_cpu);

This resulted in an attempt to send an IPI to a hot-plugging CPU that
had not initialized its reschedule vector. One option would be to make
the RCU code check to not check for CPU offline but for CPU active.
As becoming active is done after a CPU is online (in older kernels).

But Srivatsa pointed out that "the cpu_active vs cpu_online ordering has been
completely reworked - in the online path, cpu_active is set *before* cpu_online,
and also, in the cpu offline path, the cpu_active bit is reset in the CPU_DYING
notification instead of CPU_DOWN_PREPARE." Drilling in this the bring-up
path: "[brought up CPU].. send out a CPU_STARTING notification, and in response
to that, the scheduler sets the CPU in the cpu_active_mask. Again, this mask
is better left to the scheduler alone, since it has the intelligence to use it
judiciously."

The conclusion was that:
"
1. At the IPI sender side:

   It is incorrect to send an IPI to an offline CPU (cpu not present in
   the cpu_online_mask). There are numerous places where we check this
   and warn/complain.

2. At the IPI receiver side:

   It is incorrect to let the world know of our presence (by setting
   ourselves in global bitmasks) until our initialization steps are complete
   to such an extent that we can handle the consequences (such as
   receiving interrupts without crashing the sender etc.)
" (from Srivatsa)

As the native code enables the interrupts at some point we need to be
able to service them. In other words a CPU must have valid IPI vectors
if it has been marked online.

It doesn't need to handle the IPI (interrupts may be disabled) but needs
to have valid IPI vectors because another CPU may find it in cpu_online_mask
and attempt to send it an IPI.

This patch will change the order of the Xen vCPU bring-up functions so that
Xen vectors have been set up before start_secondary() is called.
It also will not continue to bring up a Xen vCPU if xen_smp_intr_init() fails
to initialize it.

Orabug 13823853
Signed-off-by Chuck Anderson <chuck.anderson@oracle.com>
Acked-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

This is based on a patch that Zhenzhong Duan had sent - which
was missing some of the remaining pieces. The kernel has the
logic to handle Xen-type-exceptions using the paravirt interface
in the assembler code (see PARAVIRT_ADJUST_EXCEPTION_FRAME -
pv_irq_ops.adjust_exception_frame and and INTERRUPT_RETURN -
pv_cpu_ops.iret).

That means the nmi handler (and other exception handlers) use
the hypervisor iret.

The other changes that would be neccessary for this would
be to translate the NMI_VECTOR to one of the entries on the
ipi_vector and make xen_send_IPI_mask_allbutself use different
events.

Fortunately for us commit 1db01b49
(xen: Clean up apic ipi interface) implemented this and we piggyback
on the cleanup such that the apic IPI interface will pass the right
vector value for NMI.

With this patch we can trigger NMIs within a PV guest (only tested
x86_64).

For this to work with normal PV guests (not initial domain)
we need the domain to be able to use the APIC ops - they are
already implemented to use the Xen event channels. For that
to be turned on in a PV domU we need to remove the masking
of X86_FEATURE_APIC.

Incidentally that means kgdb will also now work within
a PV guest without using the 'nokgdbroundup' workaround.

Note that the 32-bit version is different and this patch
does not enable that.

CC: Lisa Nguyen <lisa@xenapiadmin.com>
CC: Ben Guthro <benjamin.guthro@citrix.com>
CC: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
[v1: Fixed up per David Vrabel comments]
Reviewed-by: NBen Guthro <benjamin.guthro@citrix.com>
Reviewed-by: NDavid Vrabel <david.vrabel@citrix.com>

There's no need to do it at very early init, and doing it there
makes it impossible to use the jump_label machinery.
Signed-off-by: NJeremy Fitzhardinge <jeremy@goop.org>
Link: http://lkml.kernel.org/r/1376058122-8248-5-git-send-email-raghavendra.kt@linux.vnet.ibm.comReviewed-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: NRaghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Acked-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

The __cpuinit type of throwaway sections might have made sense
some time ago when RAM was more constrained, but now the savings
do not offset the cost and complications.  For example, the fix in
commit 5e427ec2 ("x86: Fix bit corruption at CPU resume time")
is a good example of the nasty type of bugs that can be created
with improper use of the various __init prefixes.

After a discussion on LKML[1] it was decided that cpuinit should go
the way of devinit and be phased out.  Once all the users are gone,
we can then finally remove the macros themselves from linux/init.h.

Note that some harmless section mismatch warnings may result, since
notify_cpu_starting() and cpu_up() are arch independent (kernel/cpu.c)
are flagged as __cpuinit  -- so if we remove the __cpuinit from
arch specific callers, we will also get section mismatch warnings.
As an intermediate step, we intend to turn the linux/init.h cpuinit
content into no-ops as early as possible, since that will get rid
of these warnings.  In any case, they are temporary and harmless.

This removes all the arch/x86 uses of the __cpuinit macros from
all C files.  x86 only had the one __CPUINIT used in assembly files,
and it wasn't paired off with a .previous or a __FINIT, so we can
delete it directly w/o any corresponding additional change there.

[1] https://lkml.org/lkml/2013/5/20/589

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Acked-by: NIngo Molnar <mingo@kernel.org>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NH. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>

When the user does:
echo 0 > /sys/devices/system/cpu/cpu1/online
echo 1 > /sys/devices/system/cpu/cpu1/online

kmemleak reports:
kmemleak: 7 new suspected memory leaks (see /sys/kernel/debug/kmemleak)

unreferenced object 0xffff88003fa51240 (size 32):
  comm "swapper/0", pid 1, jiffies 4294667339 (age 1027.789s)
  hex dump (first 32 bytes):
    72 65 73 63 68 65 64 31 00 00 00 00 00 00 00 00  resched1........
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff81660721>] kmemleak_alloc+0x21/0x50
    [<ffffffff81190aac>] __kmalloc_track_caller+0xec/0x2a0
    [<ffffffff812fe1bb>] kvasprintf+0x5b/0x90
    [<ffffffff812fe228>] kasprintf+0x38/0x40
    [<ffffffff81047ed1>] xen_smp_intr_init+0x41/0x2c0
    [<ffffffff816636d3>] xen_cpu_up+0x393/0x3e8
    [<ffffffff8166bbf5>] _cpu_up+0xd1/0x14b
    [<ffffffff8166bd48>] cpu_up+0xd9/0xec
    [<ffffffff81ae6e4a>] smp_init+0x4b/0xa3
    [<ffffffff81ac4981>] kernel_init_freeable+0xdb/0x1e6
    [<ffffffff8165ce39>] kernel_init+0x9/0xf0
    [<ffffffff8167edfc>] ret_from_fork+0x7c/0xb0
    [<ffffffffffffffff>] 0xffffffffffffffff

This patch fixes some of it by using the 'struct xen_common_irq->name'
field to stash away the char so that it can be freed when
the interrupt line is destroyed.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

When we free it we want to make sure to set it to a default
value of -1 so that we don't double-free it (in case somebody
calls us twice).
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

This patch adds a new structure to contain the common two things
that each of the per-cpu interrupts need:
 - an interrupt number,
 - and the name of the interrupt (to be added in 'xen/smp: Don't leak
   interrupt name when offlining').

This allows us to carry the tuple of the per-cpu interrupt data structure
and expand it as we need in the future.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

There are two functions that do a bunch of 'free_irq' on
the per_cpu IRQ. Instead of having duplicate code just move
it to one function.

This is just code movement.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

The xen_play_dead is an undead function. When the vCPU is told to
offline it ends up calling xen_play_dead wherin it calls the
VCPUOP_down hypercall which offlines the vCPU. However, when the
vCPU is onlined back, it resumes execution right after
VCPUOP_down hypercall.

That was OK (albeit the API for play_dead assumes that the CPU
stays dead and never returns) but with commit 4b0c0f29
(tick: Cleanup NOHZ per cpu data on cpu down) that is no longer safe
as said commit resets the ts->inidle which at the start of the
cpu_idle loop was set.

The net effect is that we get this warn:

Broke affinity for irq 16
installing Xen timer for CPU 1
cpu 1 spinlock event irq 48
------------[ cut here ]------------
WARNING: at /home/konrad/linux-linus/kernel/time/tick-sched.c:935 tick_nohz_idle_exit+0x195/0x1b0()
Modules linked in: dm_multipath dm_mod xen_evtchn iscsi_boot_sysfs
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 3.10.0-rc3upstream-00068-gdcdbe33a #1
Hardware name: BIOSTAR Group N61PB-M2S/N61PB-M2S, BIOS 6.00 PG 09/03/2009
 ffffffff8193b448 ffff880039da5e60 ffffffff816707c8 ffff880039da5ea0
 ffffffff8108ce8b ffff880039da4010 ffff88003fa8e500 ffff880039da4010
 0000000000000001 ffff880039da4000 ffff880039da4010 ffff880039da5eb0
Call Trace:
 [<ffffffff816707c8>] dump_stack+0x19/0x1b
 [<ffffffff8108ce8b>] warn_slowpath_common+0x6b/0xa0
 [<ffffffff8108ced5>] warn_slowpath_null+0x15/0x20
 [<ffffffff810e4745>] tick_nohz_idle_exit+0x195/0x1b0
 [<ffffffff810da755>] cpu_startup_entry+0x205/0x250
 [<ffffffff81661070>] cpu_bringup_and_idle+0x13/0x15
---[ end trace 915c8c486004dda1 ]---

b/c ts_inidle is set to zero. Thomas suggested that we just add a workaround
to call tick_nohz_idle_enter before returning from xen_play_dead() - and
that is what this patch does and fixes the issue.

We also add the stable part b/c git commit 4b0c0f29 is on the stable
tree.

CC: stable@vger.kernel.org
Suggested-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Commit f447d56d introduced the
implementation of the PV apic ipi interface. But there were some
odd things (it seems none of which cause really any issue but
maybe they should be cleaned up anyway):
 - xen_send_IPI_mask_allbutself (and by that xen_send_IPI_allbutself)
   ignore the passed in vector and only use the CALL_FUNCTION_SINGLE
   vector. While xen_send_IPI_all and xen_send_IPI_mask use the vector.
 - physflat_send_IPI_allbutself is declared unnecessarily. It is never
   used.

This patch tries to clean up those things.
Signed-off-by: NStefan Bader <stefan.bader@canonical.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

The "xen_cpu_die" and "xen_hvm_cpu_die" are very similar.
Lets coalesce them.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

There is no need to use the PV version of the IRQ_WORKER mechanism
as under PVHVM we are using the native version. The native
version is using the SMP API.

They just sit around unused:

  69:          0          0  xen-percpu-ipi       irqwork0
  83:          0          0  xen-percpu-ipi       irqwork1
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

While we don't use the spinlock interrupt line (see for details
commit f10cd522 -
xen: disable PV spinlocks on HVM) - we should still do the proper
init / deinit sequence. We did not do that correctly and for the
CPU init for PVHVM guest we would allocate an interrupt line - but
failed to deallocate the old interrupt line.

This resulted in leakage of an irq_desc but more importantly this splat
as we online an offlined CPU:

genirq: Flags mismatch irq 71. 0002cc20 (spinlock1) vs. 0002cc20 (spinlock1)
Pid: 2542, comm: init.late Not tainted 3.9.0-rc6upstream #1
Call Trace:
 [<ffffffff811156de>] __setup_irq+0x23e/0x4a0
 [<ffffffff81194191>] ? kmem_cache_alloc_trace+0x221/0x250
 [<ffffffff811161bb>] request_threaded_irq+0xfb/0x160
 [<ffffffff8104c6f0>] ? xen_spin_trylock+0x20/0x20
 [<ffffffff813a8423>] bind_ipi_to_irqhandler+0xa3/0x160
 [<ffffffff81303758>] ? kasprintf+0x38/0x40
 [<ffffffff8104c6f0>] ? xen_spin_trylock+0x20/0x20
 [<ffffffff810cad35>] ? update_max_interval+0x15/0x40
 [<ffffffff816605db>] xen_init_lock_cpu+0x3c/0x78
 [<ffffffff81660029>] xen_hvm_cpu_notify+0x29/0x33
 [<ffffffff81676bdd>] notifier_call_chain+0x4d/0x70
 [<ffffffff810bb2a9>] __raw_notifier_call_chain+0x9/0x10
 [<ffffffff8109402b>] __cpu_notify+0x1b/0x30
 [<ffffffff8166834a>] _cpu_up+0xa0/0x14b
 [<ffffffff816684ce>] cpu_up+0xd9/0xec
 [<ffffffff8165f754>] store_online+0x94/0xd0
 [<ffffffff8141d15b>] dev_attr_store+0x1b/0x20
 [<ffffffff81218f44>] sysfs_write_file+0xf4/0x170
 [<ffffffff811a2864>] vfs_write+0xb4/0x130
 [<ffffffff811a302a>] sys_write+0x5a/0xa0
 [<ffffffff8167ada9>] system_call_fastpath+0x16/0x1b
cpu 1 spinlock event irq -16
smpboot: Booting Node 0 Processor 1 APIC 0x2

And if one looks at the /proc/interrupts right after
offlining (CPU1):

  70:          0          0  xen-percpu-ipi       spinlock0
  71:          0          0  xen-percpu-ipi       spinlock1
  77:          0          0  xen-percpu-ipi       spinlock2

There is the oddity of the 'spinlock1' still being present.

CC: stable@vger.kernel.org
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

In the PVHVM path when we do CPU online/offline path we would
leak the timer%d IRQ line everytime we do a offline event. The
online path (xen_hvm_setup_cpu_clockevents via
x86_cpuinit.setup_percpu_clockev) would allocate a new interrupt
line for the timer%d.

But we would still use the old interrupt line leading to:

kernel BUG at /home/konrad/ssd/konrad/linux/kernel/hrtimer.c:1261!
invalid opcode: 0000 [#1] SMP
RIP: 0010:[<ffffffff810b9e21>]  [<ffffffff810b9e21>] hrtimer_interrupt+0x261/0x270
.. snip..
 <IRQ>
 [<ffffffff810445ef>] xen_timer_interrupt+0x2f/0x1b0
 [<ffffffff81104825>] ? stop_machine_cpu_stop+0xb5/0xf0
 [<ffffffff8111434c>] handle_irq_event_percpu+0x7c/0x240
 [<ffffffff811175b9>] handle_percpu_irq+0x49/0x70
 [<ffffffff813a74a3>] __xen_evtchn_do_upcall+0x1c3/0x2f0
 [<ffffffff813a760a>] xen_evtchn_do_upcall+0x2a/0x40
 [<ffffffff8167c26d>] xen_hvm_callback_vector+0x6d/0x80
 <EOI>
 [<ffffffff81666d01>] ? start_secondary+0x193/0x1a8
 [<ffffffff81666cfd>] ? start_secondary+0x18f/0x1a8

There is also the oddity (timer1) in the /proc/interrupts after
offlining CPU1:

  64:       1121          0  xen-percpu-virq      timer0
  78:          0          0  xen-percpu-virq      timer1
  84:          0       2483  xen-percpu-virq      timer2

This patch fixes it.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
CC: stable@vger.kernel.org

Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130321215235.486594473@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: x86@kernel.org

The PV and PVH code CPU init code share some functionality. The
PVH code ("xen/pvh: Extend vcpu_guest_context, p2m, event, and XenBus")
sets some of these up, but not all. To make it easier to read, this
patch removes the PV specific out of the generic way.

No functional change - just code movement.
Acked-by: NStefano Stabellini <stefano.stabellini@eu.citrix.com>
[v2: Fixed compile errors noticed by Fengguang Wu build system]
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

This reverts commit 41bd956d.

The fix is incorrect and not appropiate for the latest kernels.
In fact it _causes_ the BUG: scheduling while atomic while
doing vCPU hotplug.
Suggested-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Git commit 30106c17
("x86, hotplug: Support functions for CPU0 online/offline") alters what
the call to smp_store_cpu_info() does. For BSP we should use the
smp_store_boot_cpu_info() and for secondary CPU's the old
variant of smp_store_cpu_info() should be used. This fixes
the regression introduced by said commit.
Reported-and-Tested-by: NSander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

We still patch SMP instructions to UP variants if we boot with a
single CPU, but not at any other time.  In particular, not if we
unplug CPUs to return to a single cpu.

Paul McKenney points out:

 mean offline overhead is 6251/48=130.2 milliseconds.

 If I remove the alternatives_smp_switch() from the offline
 path [...] the mean offline overhead is 550/42=13.1 milliseconds

Basically, we're never going to get those 120ms back, and the
code is pretty messy.

We get rid of:

 1) The "smp-alt-once" boot option. It's actually "smp-alt-boot", the
    documentation is wrong. It's now the default.

 2) The skip_smp_alternatives flag used by suspend.

 3) arch_disable_nonboot_cpus_begin() and arch_disable_nonboot_cpus_end()
    which were only used to set this one flag.
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Cc: Paul McKenney <paul.mckenney@us.ibm.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/87vcgwwive.fsf@rustcorp.com.auSigned-off-by: NIngo Molnar <mingo@kernel.org>

ipi_call_lock/unlock() lock resp. unlock call_function.lock. This lock
protects only the call_function data structure itself, but it's
completely unrelated to cpu_online_mask. The mask to which the IPIs
are sent is calculated before call_function.lock is taken in
smp_call_function_many(), so the locking around set_cpu_online() is
pointless and can be removed.

[ tglx: Massaged changelog ]
Signed-off-by: NYong Zhang <yong.zhang0@gmail.com>
Cc: ralf@linux-mips.org
Cc: sshtylyov@mvista.com
Cc: david.daney@cavium.com
Cc: nikunj@linux.vnet.ibm.com
Cc: paulmck@linux.vnet.ibm.com
Cc: axboe@kernel.dk
Cc: peterz@infradead.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1338275765-3217-7-git-send-email-yong.zhang0@gmail.comAcked-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>