Dan Carpenter reported that the untrusted data returns from kvm_register_read()
results in the following static checker warning:
  arch/x86/kvm/lapic.c:576 kvm_pv_send_ipi()
  error: buffer underflow 'map->phys_map' 's32min-s32max'

KVM guest can easily trigger this by executing the following assembly sequence
in Ring0:

mov $10, %rax
mov $0xFFFFFFFF, %rbx
mov $0xFFFFFFFF, %rdx
mov $0, %rsi
vmcall

As this will cause KVM to execute the following code-path:
vmx_handle_exit() -> handle_vmcall() -> kvm_emulate_hypercall() -> kvm_pv_send_ipi()
which will reach out-of-bounds access.

This patch fixes it by adding a check to kvm_pv_send_ipi() against map->max_apic_id,
ignoring destinations that are not present and delivering the rest. We also check
whether or not map->phys_map[min + i] is NULL since the max_apic_id is set to the
max apic id, some phys_map maybe NULL when apic id is sparse, especially kvm
unconditionally set max_apic_id to 255 to reserve enough space for any xAPIC ID.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: NLiran Alon <liran.alon@oracle.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Liran Alon <liran.alon@oracle.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NWanpeng Li <wanpengli@tencent.com>
[Add second "if (min > map->max_apic_id)" to complete the fix. -Radim]
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

Using hypercall to send IPIs by one vmexit instead of one by one for
xAPIC/x2APIC physical mode and one vmexit per-cluster for x2APIC cluster
mode. Intel guest can enter x2apic cluster mode when interrupt remmaping
is enabled in qemu, however, latest AMD EPYC still just supports xapic
mode which can get great improvement by Exit-less IPIs. This patchset
lets a guest send multicast IPIs, with at most 128 destinations per
hypercall in 64-bit mode and 64 vCPUs per hypercall in 32-bit mode.

Hardware: Xeon Skylake 2.5GHz, 2 sockets, 40 cores, 80 threads, the VM
is 80 vCPUs, IPI microbenchmark(https://lkml.org/lkml/2017/12/19/141):

x2apic cluster mode, vanilla

 Dry-run:                         0,            2392199 ns
 Self-IPI:                  6907514,           15027589 ns
 Normal IPI:              223910476,          251301666 ns
 Broadcast IPI:                   0,         9282161150 ns
 Broadcast lock:                  0,         8812934104 ns

x2apic cluster mode, pv-ipi

 Dry-run:                         0,            2449341 ns
 Self-IPI:                  6720360,           15028732 ns
 Normal IPI:              228643307,          255708477 ns
 Broadcast IPI:                   0,         7572293590 ns  => 22% performance boost
 Broadcast lock:                  0,         8316124651 ns

x2apic physical mode, vanilla

 Dry-run:                         0,            3135933 ns
 Self-IPI:                  8572670,           17901757 ns
 Normal IPI:              226444334,          255421709 ns
 Broadcast IPI:                   0,        19845070887 ns
 Broadcast lock:                  0,        19827383656 ns

x2apic physical mode, pv-ipi

 Dry-run:                         0,            2446381 ns
 Self-IPI:                  6788217,           15021056 ns
 Normal IPI:              219454441,          249583458 ns
 Broadcast IPI:                   0,         7806540019 ns  => 154% performance boost
 Broadcast lock:                  0,         9143618799 ns

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NWanpeng Li <wanpengli@tencent.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Since swait basically implemented exclusive waits only, make sure
the API reflects that.

  $ git grep -l -e "\<swake_up\>"
		-e "\<swait_event[^ (]*"
		-e "\<prepare_to_swait\>" | while read file;
    do
	sed -i -e 's/\<swake_up\>/&_one/g'
	       -e 's/\<swait_event[^ (]*/&_exclusive/g'
	       -e 's/\<prepare_to_swait\>/&_exclusive/g' $file;
    done

With a few manual touch-ups.
Suggested-by: NLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: bigeasy@linutronix.de
Cc: oleg@redhat.com
Cc: paulmck@linux.vnet.ibm.com
Cc: pbonzini@redhat.com
Link: https://lkml.kernel.org/r/20180612083909.261946548@infradead.org

Since 4.10, commit 8003c9ae (KVM: LAPIC: add APIC Timer
periodic/oneshot mode VMX preemption timer support), guests using
periodic LAPIC timers (such as FreeBSD 8.4) would see their timers
drift significantly over time.

Differences in the underlying clocks and numerical errors means the
periods of the two timers (hv and sw) are not the same. This
difference will accumulate with every expiry resulting in a large
error between the hv and sw timer.

This means the sw timer may be running slow when compared to the hv
timer. When the timer is switched from hv to sw, the now active sw
timer will expire late. The guest VCPU is reentered and it switches to
using the hv timer. This timer catches up, injecting multiple IRQs
into the guest (of which the guest only sees one as it does not get to
run until the hv timer has caught up) and thus the guest's timer rate
is low (and becomes increasing slower over time as the sw timer lags
further and further behind).

I believe a similar problem would occur if the hv timer is the slower
one, but I have not observed this.

Fix this by synchronizing the deadlines for both timers to the same
time source on every tick. This prevents the errors from accumulating.

Fixes: 8003c9ae
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NDavid Vrabel <david.vrabel@nutanix.com>
Cc: stable@vger.kernel.org
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NWanpeng Li <wanpengli@tencent.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

Previously, we toggled between SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE
and SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES, depending on whether or
not the EXTD bit was set in MSR_IA32_APICBASE. However, if the local
APIC is disabled, we should not set either of these APIC
virtualization control bits.
Signed-off-by: NJim Mattson <jmattson@google.com>
Signed-off-by: NKrish Sadhukhan <krish.sadhukhan@oracle.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Since the commit "8003c9ae: add APIC Timer periodic/oneshot mode VMX
preemption timer support", a Windows 10 guest has some erratic timer
spikes.

Here the results on a 150000 times 1ms timer without any load:
	  Before 8003c9ae | After 8003c9ae
Max           1834us          |  86000us
Mean          1100us          |   1021us
Deviation       59us          |    149us
Here the results on a 150000 times 1ms timer with a cpu-z stress test:
	  Before 8003c9ae | After 8003c9ae
Max          32000us          | 140000us
Mean          1006us          |   1997us
Deviation      140us          |  11095us

The root cause of the problem is starting hrtimer with an expiry time
already in the past can take more than 20 milliseconds to trigger the
timer function.  It can be solved by forward such past timers
immediately, rather than submitting them to hrtimer_start().
In case the timer is periodic, update the target expiration and call
hrtimer_start with it.

v2: Check if the tsc deadline is already expired. Thank you Mika.
v3: Execute the past timers immediately rather than submitting them to
hrtimer_start().
v4: Rearm the periodic timer with advance_periodic_target_expiration() a
simpler version of set_target_expiration(). Thank you Paolo.

Cc: Mika Penttilä <mika.penttila@nextfour.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: NAnthoine Bourgeois <anthoine.bourgeois@blade-group.com>
8003c9ae ("KVM: LAPIC: add APIC Timer periodic/oneshot mode VMX preemption timer support")
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

Devices which use level-triggered interrupts under Windows 2016 with
Hyper-V role enabled don't work: Windows disables EOI broadcast in SPIV
unconditionally. Our in-kernel IOAPIC implementation emulates an old IOAPIC
version which has no EOI register so EOI never happens.

The issue was discovered and discussed a while ago:
https://www.spinics.net/lists/kvm/msg148098.html

While this is a guest OS bug (it should check that IOAPIC has the required
capabilities before disabling EOI broadcast) we can workaround it in KVM:
advertising DIRECTED_EOI with in-kernel IOAPIC makes little sense anyway.
Signed-off-by: NVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

Moving the code around broke this rare configuration.
Use this opportunity to finally call lapic reset from vcpu reset.

Reported-by: syzbot+fb7a33a4b6c35007a72b@syzkaller.appspotmail.com
Suggested-by: NPaolo Bonzini <pbonzini@redhat.com>
Fixes: 0b2e9904 ("KVM: x86: move LAPIC initialization after VMCS creation")
Cc: stable@vger.kernel.org
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

The initial reset of the local APIC is performed before the VMCS has been
created, but it tries to do a vmwrite:

 vmwrite error: reg 810 value 4a00 (err 18944)
 CPU: 54 PID: 38652 Comm: qemu-kvm Tainted: G        W I      4.16.0-0.rc2.git0.1.fc28.x86_64 #1
 Hardware name: Intel Corporation S2600CW/S2600CW, BIOS SE5C610.86B.01.01.0003.090520141303 09/05/2014
 Call Trace:
  vmx_set_rvi [kvm_intel]
  vmx_hwapic_irr_update [kvm_intel]
  kvm_lapic_reset [kvm]
  kvm_create_lapic [kvm]
  kvm_arch_vcpu_init [kvm]
  kvm_vcpu_init [kvm]
  vmx_create_vcpu [kvm_intel]
  kvm_vm_ioctl [kvm]

Move it later, after the VMCS has been created.

Fixes: 4191db26 ("KVM: x86: Update APICv on APIC reset")
Cc: stable@vger.kernel.org
Cc: Liran Alon <liran.alon@oracle.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

This commit doesn't change semantics.
It is done as a preparation for future commits.
Signed-off-by: NLiran Alon <liran.alon@oracle.com>
Reviewed-by: NNikita Leshenko <nikita.leshchenko@oracle.com>
Reviewed-by: NLiam Merwick <liam.merwick@oracle.com>
Signed-off-by: NLiam Merwick <liam.merwick@oracle.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

sync_pir_to_irr() is only called if vcpu->arch.apicv_active()==true.
In case it is false, VMX code make sure to set sync_pir_to_irr
to NULL.

Therefore, having SVM stubs allows to remove check for if
sync_pir_to_irr != NULL from all calling sites.
Signed-off-by: NLiran Alon <liran.alon@oracle.com>
Suggested-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NNikita Leshenko <nikita.leshchenko@oracle.com>
Reviewed-by: NLiam Merwick <liam.merwick@oracle.com>
[Return highest IRR in the SVM case. - Paolo]
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

In x2apic mode the LDR is fixed based on the ID rather
than separately loadable like it was before x2.
When kvm_apic_set_state is called, the base is set, and if
it has the X2APIC_ENABLE flag set then the LDR is calculated;
however that value gets overwritten by the memcpy a few lines
below overwriting it with the value that came from userland.

The symptom is a lack of EOI after loading the state
(e.g. after a QEMU migration) and is due to the EOI bitmap
being wrong due to the incorrect LDR.  This was seen with
a Win2016 guest under Qemu with irqchip=split whose USB mouse
didn't work after a VM migration.

This corresponds to RH bug:
  https://bugzilla.redhat.com/show_bug.cgi?id=1502591Reported-by: NYiqian Wei <yiwei@redhat.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Cc: stable@vger.kernel.org
[Applied fixup from Liran Alon. - Paolo]
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Split out the ldr calculation from kvm_apic_set_x2apic_id
since we're about to reuse it in the following patch.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

In kvm_apic_set_state() we update the hardware virtualized APIC after
the full APIC state has been overwritten. Do the same, when the full
APIC state has been reset in kvm_lapic_reset().

This updates some hardware state that was previously forgotten, as
far as I can tell. Also, this allows removing some APIC-related reset
code from vmx_vcpu_reset().
Signed-off-by: NJan H. Schönherr <jschoenh@amazon.de>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Our routines look at tscdeadline and period when deciding state of a
timer.  The timer is disarmed when switching between TSC deadline and
other modes, so we should set everything to disarmed state.
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
Reviewed-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

preemption timer only looks at tscdeadline and could inject already
disarmed timer.
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
Reviewed-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

0 should disable the timer, but start_hv_timer will recognize it as an
expired timer instead.
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
Reviewed-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The description in the Intel SDM of how the divide configuration
register is used: "The APIC timer frequency will be the processor's bus
clock or core crystal clock frequency divided by the value specified in
the divide configuration register."

Observation of baremetal shown that when the TDCR is change, the TMCCT
does not change or make a big jump in value, but the rate at which it
count down change.

The patch update the emulation to APIC timer to so that a change to the
divide configuration would be reflected in the value of the counter and
when the next interrupt is triggered.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
[Fixed some whitespace and added a check for negative delta and running
 timer. - Radim]
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

If we take TSC-deadline mode timer out of the picture, the Intel SDM
does not say that the timer is disable when the timer mode is change,
either from one-shot to periodic or vice versa.

After this patch, the timer is no longer disarmed on change of mode, so
the counter (TMCCT) keeps counting down.

So what does a write to LVTT changes ? On baremetal, the change of mode
is probably taken into account only when the counter reach 0. When this
happen, LVTT is use to figure out if the counter should restard counting
down from TMICT (so periodic mode) or stop counting (if one-shot mode).

This patch is based on observation of the behavior of the APIC timer on
baremetal as well as check that they does not go against the description
written in the Intel SDM.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
[Fixed rate limiting of periodic timer.]
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

Extract the logic of limit lapic periodic timer frequency to a new function,
this function will be used by later patches.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

SDM 10.5.4.1 TSC-Deadline Mode mentioned that "Transitioning between TSC-Deadline
mode and other timer modes also disarms the timer". So the APIC Timer Initial Count
Register for one-shot/periodic mode should be reset. This patch do it.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
[Removed unnecessary definition of APIC_LVT_TIMER_MASK.]
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

A comment might serve future readers.
Signed-off-by: NDavidlohr Bueso <dbueso@suse.de>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

It has been experimentally confirmed that supporting these two MSRs is one
of the necessary conditions for nested Hyper-V to use the TSC page. Modern
Windows guests are noticeably slower when they fall back to reading
timestamps from the HV_X64_MSR_TIME_REF_COUNT MSR instead of using the TSC
page.

The newly supported MSRs are advertised with the AccessFrequencyRegs
partition privilege flag and CPUID.40000003H:EDX[8] "Support for
determining timer frequencies is available" (both outside of the scope of
this KVM patch).
Reviewed-by: NRadim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NLadi Prosek <lprosek@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Preempt can occur in the preemption timer expiration handler:

          CPU0                    CPU1

  preemption timer vmexit
  handle_preemption_timer(vCPU0)
    kvm_lapic_expired_hv_timer
      hv_timer_is_use == true
  sched_out
                           sched_in
                           kvm_arch_vcpu_load
                             kvm_lapic_restart_hv_timer
                               restart_apic_timer
                                 start_hv_timer
                                   already-expired timer or sw timer triggerd in the window
                                 start_sw_timer
                                   cancel_hv_timer
                           /* back in kvm_lapic_expired_hv_timer */
                           cancel_hv_timer
                             WARN_ON(!apic->lapic_timer.hv_timer_in_use);  ==> Oops

This can be reproduced if CONFIG_PREEMPT is enabled.

------------[ cut here ]------------
 WARNING: CPU: 4 PID: 2972 at /home/kernel/linux/arch/x86/kvm//lapic.c:1563 kvm_lapic_expired_hv_timer+0x9e/0xb0 [kvm]
 CPU: 4 PID: 2972 Comm: qemu-system-x86 Tainted: G           OE   4.13.0-rc2+ #16
 RIP: 0010:kvm_lapic_expired_hv_timer+0x9e/0xb0 [kvm]
Call Trace:
  handle_preemption_timer+0xe/0x20 [kvm_intel]
  vmx_handle_exit+0xb8/0xd70 [kvm_intel]
  kvm_arch_vcpu_ioctl_run+0xdd1/0x1be0 [kvm]
  ? kvm_arch_vcpu_load+0x47/0x230 [kvm]
  ? kvm_arch_vcpu_load+0x62/0x230 [kvm]
  kvm_vcpu_ioctl+0x340/0x700 [kvm]
  ? kvm_vcpu_ioctl+0x340/0x700 [kvm]
  ? __fget+0xfc/0x210
  do_vfs_ioctl+0xa4/0x6a0
  ? __fget+0x11d/0x210
  SyS_ioctl+0x79/0x90
  do_syscall_64+0x81/0x220
  entry_SYSCALL64_slow_path+0x25/0x25
 ------------[ cut here ]------------
 WARNING: CPU: 4 PID: 2972 at /home/kernel/linux/arch/x86/kvm//lapic.c:1498 cancel_hv_timer.isra.40+0x4f/0x60 [kvm]
 CPU: 4 PID: 2972 Comm: qemu-system-x86 Tainted: G        W  OE   4.13.0-rc2+ #16
 RIP: 0010:cancel_hv_timer.isra.40+0x4f/0x60 [kvm]
Call Trace:
  kvm_lapic_expired_hv_timer+0x3e/0xb0 [kvm]
  handle_preemption_timer+0xe/0x20 [kvm_intel]
  vmx_handle_exit+0xb8/0xd70 [kvm_intel]
  kvm_arch_vcpu_ioctl_run+0xdd1/0x1be0 [kvm]
  ? kvm_arch_vcpu_load+0x47/0x230 [kvm]
  ? kvm_arch_vcpu_load+0x62/0x230 [kvm]
  kvm_vcpu_ioctl+0x340/0x700 [kvm]
  ? kvm_vcpu_ioctl+0x340/0x700 [kvm]
  ? __fget+0xfc/0x210
  do_vfs_ioctl+0xa4/0x6a0
  ? __fget+0x11d/0x210
  SyS_ioctl+0x79/0x90
  do_syscall_64+0x81/0x220
  entry_SYSCALL64_slow_path+0x25/0x25

This patch fixes it by making the caller of cancel_hv_timer, start_hv_timer
and start_sw_timer be in preemption-disabled regions, which trivially
avoid any reentrancy issue with preempt notifier.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
[Add more WARNs. - Paolo]
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

If the TSC deadline timer is programmed really close to the deadline or
even in the past, the computation in vmx_set_hv_timer will program the
absolute target tsc value to vmcs preemption timer field w/ delta == 0,
then plays a vmentry and an upcoming vmx preemption timer fire vmexit
dance, the lapic timer injection is delayed due to this duration. Actually
the lapic timer which is emulated by hrtimer can handle this correctly.

This patch fixes it by firing the lapic timer and injecting a timer interrupt
immediately during the next vmentry if the TSC deadline timer is programmed
really close to the deadline or even in the past. This saves ~300 cycles on
the tsc_deadline_timer test of apic.flat.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Move the code to cancel the hv timer into the caller, just before
it starts the hrtimer.  Check availability of the hv timer in
start_hv_timer.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

There are many cases in which the hv timer must be canceled.  Split out
a new function to avoid duplication.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Intel SDM says, that at most one LAPIC should be configured with ExtINT
delivery. KVM configures all LAPICs this way. This causes pic_unlock()
to kick the first available vCPU from the internal KVM data structures.
If this vCPU is not the BSP, but some not-yet-booted AP, the BSP may
never realize that there is an interrupt.

Fix that by enabling ExtINT delivery only for the BSP.

This allows booting a Linux guest without a TSC in the above situation.
Otherwise the BSP gets stuck in calibrate_delay_converge().
Signed-off-by: NJan H. Schönherr <jschoenh@amazon.de>
Reviewed-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Preemption can occur during cancel preemption timer, and there will be
inconsistent status in lapic, vmx and vmcs field.

          CPU0                    CPU1

  preemption timer vmexit
  handle_preemption_timer(vCPU0)
    kvm_lapic_expired_hv_timer
      vmx_cancel_hv_timer
        vmx->hv_deadline_tsc = -1
        vmcs_clear_bits
        /* hv_timer_in_use still true */
  sched_out
                           sched_in
                           kvm_arch_vcpu_load
                             vmx_set_hv_timer
                               write vmx->hv_deadline_tsc
                               vmcs_set_bits
                           /* back in kvm_lapic_expired_hv_timer */
                           hv_timer_in_use = false
                           ...
                           vmx_vcpu_run
                             vmx_arm_hv_run
                               write preemption timer deadline
                             spurious preemption timer vmexit
                               handle_preemption_timer(vCPU0)
                                 kvm_lapic_expired_hv_timer
                                   WARN_ON(!apic->lapic_timer.hv_timer_in_use);

This can be reproduced sporadically during boot of L2 on a
preemptible L1, causing a splat on L1.

 WARNING: CPU: 3 PID: 1952 at arch/x86/kvm/lapic.c:1529 kvm_lapic_expired_hv_timer+0xb5/0xd0 [kvm]
 CPU: 3 PID: 1952 Comm: qemu-system-x86 Not tainted 4.12.0-rc1+ #24 RIP: 0010:kvm_lapic_expired_hv_timer+0xb5/0xd0 [kvm]
  Call Trace:
  handle_preemption_timer+0xe/0x20 [kvm_intel]
  vmx_handle_exit+0xc9/0x15f0 [kvm_intel]
  ? lock_acquire+0xdb/0x250
  ? lock_acquire+0xdb/0x250
  ? kvm_arch_vcpu_ioctl_run+0xdf3/0x1ce0 [kvm]
  kvm_arch_vcpu_ioctl_run+0xe55/0x1ce0 [kvm]
  kvm_vcpu_ioctl+0x384/0x7b0 [kvm]
  ? kvm_vcpu_ioctl+0x384/0x7b0 [kvm]
  ? __fget+0xf3/0x210
  do_vfs_ioctl+0xa4/0x700
  ? __fget+0x114/0x210
  SyS_ioctl+0x79/0x90
  do_syscall_64+0x8f/0x750
  ? trace_hardirqs_on_thunk+0x1a/0x1c
  entry_SYSCALL64_slow_path+0x25/0x25

This patch fixes it by disabling preemption while cancelling
preemption timer.  This way cancel_hv_timer is atomic with
respect to kvm_arch_vcpu_load.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Patch series "kvmalloc", v5.

There are many open coded kmalloc with vmalloc fallback instances in the
tree.  Most of them are not careful enough or simply do not care about
the underlying semantic of the kmalloc/page allocator which means that
a) some vmalloc fallbacks are basically unreachable because the kmalloc
part will keep retrying until it succeeds b) the page allocator can
invoke a really disruptive steps like the OOM killer to move forward
which doesn't sound appropriate when we consider that the vmalloc
fallback is available.

As it can be seen implementing kvmalloc requires quite an intimate
knowledge if the page allocator and the memory reclaim internals which
strongly suggests that a helper should be implemented in the memory
subsystem proper.

Most callers, I could find, have been converted to use the helper
instead.  This is patch 6.  There are some more relying on __GFP_REPEAT
in the networking stack which I have converted as well and Eric Dumazet
was not opposed [2] to convert them as well.

[1] http://lkml.kernel.org/r/20170130094940.13546-1-mhocko@kernel.org
[2] http://lkml.kernel.org/r/1485273626.16328.301.camel@edumazet-glaptop3.roam.corp.google.com

This patch (of 9):

Using kmalloc with the vmalloc fallback for larger allocations is a
common pattern in the kernel code.  Yet we do not have any common helper
for that and so users have invented their own helpers.  Some of them are
really creative when doing so.  Let's just add kv[mz]alloc and make sure
it is implemented properly.  This implementation makes sure to not make
a large memory pressure for > PAGE_SZE requests (__GFP_NORETRY) and also
to not warn about allocation failures.  This also rules out the OOM
killer as the vmalloc is a more approapriate fallback than a disruptive
user visible action.

This patch also changes some existing users and removes helpers which
are specific for them.  In some cases this is not possible (e.g.
ext4_kvmalloc, libcfs_kvzalloc) because those seems to be broken and
require GFP_NO{FS,IO} context which is not vmalloc compatible in general
(note that the page table allocation is GFP_KERNEL).  Those need to be
fixed separately.

While we are at it, document that __vmalloc{_node} about unsupported gfp
mask because there seems to be a lot of confusion out there.
kvmalloc_node will warn about GFP_KERNEL incompatible (which are not
superset) flags to catch new abusers.  Existing ones would have to die
slowly.

[sfr@canb.auug.org.au: f2fs fixup]
  Link: http://lkml.kernel.org/r/20170320163735.332e64b7@canb.auug.org.au
Link: http://lkml.kernel.org/r/20170306103032.2540-2-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>	[ext4 part]
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This reverts commit bbd64115.

I've been sitting on this revert for too long and it unfortunately
missed 4.11.  It's also the reason why I haven't merged ring-based
dirty tracking for 4.12.

Using kvm_vcpu_memslots in kvm_gfn_to_hva_cache_init and
kvm_vcpu_write_guest_offset_cached means that the MSR value can
now be used to access SMRAM, simply by making it point to an SMRAM
physical address.  This is problematic because it lets the guest
OS overwrite memory that it shouldn't be able to touch.

Cc: stable@vger.kernel.org
Fixes: bbd64115Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Provide versions of struct gfn_to_hva_cache functions that
take vcpu as a parameter instead of struct kvm.  The existing functions
are not needed anymore, so delete them.  This allows dirty pages to
be logged in the vcpu dirty ring, instead of the global dirty ring,
for ring-based dirty memory tracking.
Signed-off-by: NLei Cao <lei.cao@stratus.com>
Message-Id: <CY1PR08MB19929BD2AC47A291FD680E83F04F0@CY1PR08MB1992.namprd08.prod.outlook.com>
Reviewed-by: NRadim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Since bf9f6ac8 ("KVM: Update Posted-Interrupts Descriptor when vCPU
is blocked", 2015-09-18) the posted interrupt descriptor is checked
unconditionally for PIR.ON.  Therefore we don't need KVM_REQ_EVENT to
trigger the scan and, if NMIs or SMIs are not involved, we can avoid
the complicated event injection path.

Calling kvm_vcpu_kick if PIR.ON=1 is also useless, though it has been
there since APICv was introduced.

However, without the KVM_REQ_EVENT safety net KVM needs to be much
more careful about races between vmx_deliver_posted_interrupt and
vcpu_enter_guest.  First, the IPI for posted interrupts may be issued
between setting vcpu->mode = IN_GUEST_MODE and disabling interrupts.
If that happens, kvm_trigger_posted_interrupt returns true, but
smp_kvm_posted_intr_ipi doesn't do anything about it.  The guest is
entered with PIR.ON, but the posted interrupt IPI has not been sent
and the interrupt is only delivered to the guest on the next vmentry
(if any).  To fix this, disable interrupts before setting vcpu->mode.
This ensures that the IPI is delayed until the guest enters non-root mode;
it is then trapped by the processor causing the interrupt to be injected.

Second, the IPI may be issued between kvm_x86_ops->sync_pir_to_irr(vcpu)
and vcpu->mode = IN_GUEST_MODE.  In this case, kvm_vcpu_kick is called
but it (correctly) doesn't do anything because it sees vcpu->mode ==
OUTSIDE_GUEST_MODE.  Again, the guest is entered with PIR.ON but no
posted interrupt IPI is pending; this time, the fix for this is to move
the RVI update after IN_GUEST_MODE.

Both issues were mostly masked by the liberal usage of KVM_REQ_EVENT,
though the second could actually happen with VT-d posted interrupts.
In both race scenarios KVM_REQ_EVENT would cancel guest entry, resulting
in another vmentry which would inject the interrupt.

This saves about 300 cycles on the self_ipi_* tests of vmexit.flat.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Calls to apic_find_highest_irr are scanning IRR twice, once
in vmx_sync_pir_from_irr and once in apic_search_irr.  Change
sync_pir_from_irr to get the new maximum IRR from kvm_apic_update_irr;
now that it does the computation, it can also do the RVI write.

In order to avoid complications in svm.c, make the callback optional.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Add return value to __kvm_apic_update_irr/kvm_apic_update_irr.
Move vmx_sync_pir_to_irr around.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Pending interrupts might be in the PI descriptor when the
LAPIC is restored from an external state; we do not want
them to be injected.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

KVM's lapic emulation uses static_key_deferred (apic_{hw,sw}_disabled).
These are implemented with delayed_work structs which can still be
pending when the KVM module is unloaded. We've seen this cause kernel
panics when the kvm_intel module is quickly reloaded.

Use the new static_key_deferred_flush() API to flush pending updates on
module unload.
Signed-off-by: NDavid Matlack <dmatlack@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

On interrupt delivery the PPR can only grow (except for auto-EOI),
so it is impossible that non-auto-EOI interrupt delivery results
in KVM_REQ_EVENT.  We can therefore use __apic_update_ppr.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

On PPR update, we set KVM_REQ_EVENT unconditionally anytime PPR is lowered.
But we can take into account IRR here already.
Reviewed-by: NRoman Kagan <rkagan@virtuozzo.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>