Matt Evans spotted that x86 bpf_jit was incorrectly handling negative
constant offsets in BPF_S_LDX_B_MSH instruction.

We need to abort JIT compilation like we do in common_load so that
filter uses the interpreter code and can call __load_pointer()

Reference: http://lists.openwall.net/netdev/2011/07/19/11

Thanks to Indan Zupancic to bring back this issue.
Reported-by: NMatt Evans <matt@ozlabs.org>
Reported-by: NIndan Zupancic <indan@nul.nu>
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Verified using the below proglet.. before:

[root@westmere ~]# perf stat -e node-stores -e node-store-misses ./numa 0
remote write

 Performance counter stats for './numa 0':

         2,101,554 node-stores
         2,096,931 node-store-misses

       5.021546079 seconds time elapsed

[root@westmere ~]# perf stat -e node-stores -e node-store-misses ./numa 1
local write

 Performance counter stats for './numa 1':

           501,137 node-stores
               199 node-store-misses

       5.124451068 seconds time elapsed

After:

[root@westmere ~]# perf stat -e node-stores -e node-store-misses ./numa 0
remote write

 Performance counter stats for './numa 0':

         2,107,516 node-stores
         2,097,187 node-store-misses

       5.012755149 seconds time elapsed

[root@westmere ~]# perf stat -e node-stores -e node-store-misses ./numa 1
local write

 Performance counter stats for './numa 1':

         2,063,355 node-stores
               165 node-store-misses

       5.082091494 seconds time elapsed

#define _GNU_SOURCE

#include <sched.h>
#include <stdio.h>
#include <errno.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <dirent.h>
#include <signal.h>
#include <unistd.h>
#include <numaif.h>
#include <stdlib.h>

#define SIZE (32*1024*1024)

volatile int done;

void sig_done(int sig)
{
	done = 1;
}

int main(int argc, char **argv)
{
	cpu_set_t *mask, *mask2;
	size_t size;
	int i, err, t;
	int nrcpus = 1024;
	char *mem;
	unsigned long nodemask = 0x01; /* node 0 */
	DIR *node;
	struct dirent *de;
	int read = 0;
	int local = 0;

	if (argc < 2) {
		printf("usage: %s [0-3]\n", argv[0]);
		printf("  bit0 - local/remote\n");
		printf("  bit1 - read/write\n");
		exit(0);
	}

	switch (atoi(argv[1])) {
	case 0:
		printf("remote write\n");
		break;
	case 1:
		printf("local write\n");
		local = 1;
		break;
	case 2:
		printf("remote read\n");
		read = 1;
		break;
	case 3:
		printf("local read\n");
		local = 1;
		read = 1;
		break;
	}

	mask = CPU_ALLOC(nrcpus);
	size = CPU_ALLOC_SIZE(nrcpus);
	CPU_ZERO_S(size, mask);

	node = opendir("/sys/devices/system/node/node0/");
	if (!node)
		perror("opendir");
	while ((de = readdir(node))) {
		int cpu;

		if (sscanf(de->d_name, "cpu%d", &cpu) == 1)
			CPU_SET_S(cpu, size, mask);
	}
	closedir(node);

	mask2 = CPU_ALLOC(nrcpus);
	CPU_ZERO_S(size, mask2);
	for (i = 0; i < size; i++)
		CPU_SET_S(i, size, mask2);
	CPU_XOR_S(size, mask2, mask2, mask); // invert

	if (!local)
		mask = mask2;

	err = sched_setaffinity(0, size, mask);
	if (err)
		perror("sched_setaffinity");

	mem = mmap(0, SIZE, PROT_READ|PROT_WRITE,
			MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
	err = mbind(mem, SIZE, MPOL_BIND, &nodemask, 8*sizeof(nodemask), MPOL_MF_MOVE);
	if (err)
		perror("mbind");

	signal(SIGALRM, sig_done);
	alarm(5);

	if (!read) {
		while (!done) {
			for (i = 0; i < SIZE; i++)
				mem[i] = 0x01;
		}
	} else {
		while (!done) {
			for (i = 0; i < SIZE; i++)
				t += *(volatile char *)(mem + i);
		}
	}

	return 0;
}
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Cc: <stable@kernel.org>
Link: http://lkml.kernel.org/n/tip-tq73sxus35xmqpojf7ootxgs@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@elte.hu>

Commit f0fbf0ab ("x86: integrate delay functions") converted
delay_tsc() into a random delay generator for 64 bit.  The reason is
that it merged the mostly identical versions of delay_32.c and
delay_64.c.  Though the subtle difference of the result was:

 static void delay_tsc(unsigned long loops)
 {
-	unsigned bclock, now;
+	unsigned long bclock, now;

Now the function uses rdtscl() which returns the lower 32bit of the
TSC. On 32bit that's not problematic as unsigned long is 32bit. On 64
bit this fails when the lower 32bit are close to wrap around when
bclock is read, because the following check

       if ((now - bclock) >= loops)
       	  	break;

evaluated to true on 64bit for e.g. bclock = 0xffffffff and now = 0
because the unsigned long (now - bclock) of these values results in
0xffffffff00000001 which is definitely larger than the loops
value. That explains Tvortkos observation:

"Because I am seeing udelay(500) (_occasionally_) being short, and
 that by delaying for some duration between 0us (yep) and 491us."

Make those variables explicitely u32 again, so this works for both 32
and 64 bit.
Reported-by: NTvrtko Ursulin <tvrtko.ursulin@onelan.co.uk>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org # >= 2.6.27
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

It turns out that test-compiling this file on x86-64 doesn't really
help, because much of it is x86-32-specific.  And so I hadn't noticed
the slightly over-eager removal of the 'r' from 'addr' variable despite
thinking I had tested it.
Signed-off-by: NLinus "oopsie" Torvalds <torvalds@linux-foundation.org>

Several users of "find_vma_prev()" were not in fact interested in the
previous vma if there was no primary vma to be found either.  And in
those cases, we're much better off just using the regular "find_vma()",
and then "prev" can be looked up by just checking vma->vm_prev.

The find_vma_prev() semantics are fairly subtle (see Mikulas' recent
commit 83cd904d: "mm: fix find_vma_prev"), and the whole "return
prev by reference" means that it generates worse code too.

Thus this "let's avoid using this inconvenient and clearly too subtle
interface when we don't really have to" patch.

Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

It turned out that a performance counter on AMD does not
count at all when the GO or HO bit is set in the control
register and SVM is disabled in EFER.

This patch works around this issue by masking out the HO bit
in the performance counter control register when SVM is not
enabled.

The GO bit is not touched because it is only set when the
user wants to count in guest-mode only. So when SVM is
disabled the counter should not run at all and the
not-counting is the intended behaviour.
Signed-off-by: NJoerg Roedel <joerg.roedel@amd.com>
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Avi Kivity <avi@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Robert Richter <robert.richter@amd.com>
Cc: stable@vger.kernel.org # v3.2
Link: http://lkml.kernel.org/r/1330523852-19566-1-git-send-email-joerg.roedel@amd.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

Carlos was getting

	WARNING: at drivers/pci/pci.c:118 pci_ioremap_bar+0x24/0x52()

when probing his sound card, and sound did not work.  After adding
pci=use_crs to the kernel command line, no more trouble.

Ok, we can add a quirk.  dmidecode output reveals that this is an MSI
MS-7253, for which we already have a quirk, but the short-sighted
author tied the quirk to a single BIOS version, making it not kick in
on Carlos's machine with BIOS V1.2.  If a later BIOS update makes it
no longer necessary to look at the _CRS info it will still be
harmless, so let's stop trying to guess which versions have and don't
have accurate _CRS tables.

Addresses https://bugtrack.alsa-project.org/alsa-bug/view.php?id=5533
Also see <https://bugzilla.kernel.org/show_bug.cgi?id=42619>.
Reported-by: NCarlos Luna <caralu74@gmail.com>
Reviewed-by: NBjorn Helgaas <bhelgaas@google.com>
Signed-off-by: NJonathan Nieder <jrnieder@gmail.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

In the spirit of commit 29cf7a30 ("x86/PCI: use host bridge _CRS
info on ASUS M2V-MX SE"), this DMI quirk turns on "pci_use_crs" by
default on a board that needs it.

This fixes boot failures and oopses introduced in 3e3da00c
("x86/pci: AMD one chain system to use pci read out res").  The quirk
is quite targetted (to a specific board and BIOS version) for two
reasons:

 (1) to emphasize that this method of tackling the problem one quirk
     at a time is a little insane

 (2) to give BIOS vendors an opportunity to use simpler tables and
     allow us to return to generic behavior (whatever that happens to
     be) with a later BIOS update

In other words, I am not at all happy with having quirks like this.
But it is even worse for the kernel not to work out of the box on
these machines, so...

Reference: https://bugzilla.kernel.org/show_bug.cgi?id=42619Reported-by: NSvante Signell <svante.signell@telia.com>
Signed-off-by: NJonathan Nieder <jrnieder@gmail.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

warning:
unreferenced object 0xffff8801f6914200 (size 512):
  comm "swapper/0", pid 1, jiffies 4294893643 (age 2664.644s)
  hex dump (first 32 bytes):
    00 00 c0 fe 00 00 00 00 ff ff ff ff 00 00 00 00  ................
    60 58 2f f6 03 88 ff ff 00 02 00 00 00 00 00 00  `X/.............
  backtrace:
    [<ffffffff81c2408c>] kmemleak_alloc+0x26/0x43
    [<ffffffff8113764f>] __kmalloc+0x121/0x183
    [<ffffffff81ca8d93>] get_current_resources+0x5a/0xc6
    [<ffffffff81c5bedd>] pci_acpi_scan_root+0x13c/0x21c
    [<ffffffff81c2a745>] acpi_pci_root_add+0x1e1/0x421
    [<ffffffff81408f50>] acpi_device_probe+0x50/0x190
    [<ffffffff8149edc7>] really_probe+0x99/0x126
    [<ffffffff8149ef83>] driver_probe_device+0x3b/0x56
    [<ffffffff8149effd>] __driver_attach+0x5f/0x82
    [<ffffffff8149d860>] bus_for_each_dev+0x5c/0x88
    [<ffffffff8149eb87>] driver_attach+0x1e/0x20
    [<ffffffff8149e7cc>] bus_add_driver+0xca/0x21d
    [<ffffffff8149f47b>] driver_register+0x91/0xfe
    [<ffffffff81409d09>] acpi_bus_register_driver+0x43/0x45
    [<ffffffff8278bdc9>] acpi_pci_root_init+0x20/0x28
    [<ffffffff810001e7>] do_one_initcall+0x57/0x134

The system has _CRS for root buses, but they are not used because the machine
date is before the cutoff date for _CRS usage.

Try to free those unused resource arrays and names.
Reviewed-by: NBjorn Helgaas <bhelgaas@google.com>
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

141168c3 ("x86: Simplify code by removing a !SMP #ifdefs
from 'struct cpuinfo_x86'") removed a bunch of CONFIG_SMP ifdefs
around code touching struct cpuinfo_x86 members but also caused
the following build error with Randy's randconfigs:

mce_amd.c:(.cpuinit.text+0x4723): undefined reference to `cpu_llc_shared_map'

Restore the #ifdef in threshold_create_bank() which creates
symlinks on the non-BSP CPUs.

There's a better patch series being worked on by Kevin Winchester
which will solve this in a cleaner fashion, but that series is
too ambitious for v3.3 merging - so we first queue up this trivial
fix and then do the rest for v3.4.
Signed-off-by: NBorislav Petkov <bp@alien8.de>
Acked-by: NKevin Winchester <kjwinchester@gmail.com>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: Nick Bowler <nbowler@elliptictech.com>
Link: http://lkml.kernel.org/r/20120203191801.GA2846@x1.osrc.amd.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

(And define it properly for x86-32, which had its 'current_task'
declaration in separate from x86-64)

Bitten by my dislike for modules on the machines I use, and the fact
that apparently nobody else actually wanted to test the patches I sent
out.

Snif. Nobody else cares.

Anyway, we probably should uninline the 'kernel_fpu_begin()' function
that is what modules actually use and that references this, but this is
the minimal fix for now.
Reported-by: NJosh Boyer <jwboyer@gmail.com>
Reported-and-tested-by: NJongman Heo <jongman.heo@samsung.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Linus noticed that the cmp used to check if the code segment is
__KERNEL_CS or not did not specify a size. Perhaps it does not matter
as H. Peter Anvin noted that user space can not set the bottom two
bits of the %cs register. But it's best not to let the assembly choose
and change things between different versions of gas, but instead just
pick the size.

Four bytes are used to compare the saved code segment against
__KERNEL_CS. Perhaps this might mess up Xen, but we can fix that when
the time comes.

Also I noticed that there was another non-specified cmp that checks
the special stack variable if it is 1 or 0. This too probably doesn't
matter what cmp is used, but this patch uses cmpl just to make it non
ambiguous.

Link: http://lkml.kernel.org/r/CA+55aFxfAn9MWRgS3O5k2tqN5ys1XrhSFVO5_9ZAoZKDVgNfGA@mail.gmail.comSuggested-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

This makes us recognize when we try to restore FPU state that matches
what we already have in the FPU on this CPU, and avoids the restore
entirely if so.

To do this, we add two new data fields:

 - a percpu 'fpu_owner_task' variable that gets written any time we
   update the "has_fpu" field, and thus acts as a kind of back-pointer
   to the task that owns the CPU.  The exception is when we save the FPU
   state as part of a context switch - if the save can keep the FPU
   state around, we leave the 'fpu_owner_task' variable pointing at the
   task whose FP state still remains on the CPU.

 - a per-thread 'last_cpu' field, that indicates which CPU that thread
   used its FPU on last.  We update this on every context switch
   (writing an invalid CPU number if the last context switch didn't
   leave the FPU in a lazily usable state), so we know that *that*
   thread has done nothing else with the FPU since.

These two fields together can be used when next switching back to the
task to see if the CPU still matches: if 'fpu_owner_task' matches the
task we are switching to, we know that no other task (or kernel FPU
usage) touched the FPU on this CPU in the meantime, and if the current
CPU number matches the 'last_cpu' field, we know that this thread did no
other FP work on any other CPU, so the FPU state on the CPU must match
what was saved on last context switch.

In that case, we can avoid the 'f[x]rstor' entirely, and just clear the
CR0.TS bit.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This inlines what is usually just a couple of instructions, but more
importantly it also fixes the theoretical error case (can that FPU
restore really ever fail? Maybe we should remove the checking).

We can't start sending signals from within the scheduler, we're much too
deep in the kernel and are holding the runqueue lock etc.  So don't
bother even trying.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This makes sure we clear the FPU usage counter for newly created tasks,
just so that we start off in a known state (for example, don't try to
preload the FPU state on the first task switch etc).

It also fixes a thinko in when we increment the fpu_counter at task
switch time, introduced by commit 34ddc81a ("i387: re-introduce FPU
state preloading at context switch time").  We should increment the
*new* task fpu_counter, not the old task, and only if we decide to use
that state (whether lazily or preloaded).
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

[Pls also look at https://lkml.org/lkml/2012/2/10/228]

Using of PAT to change pages from WB to WC works quite nicely.
Changing it back to WB - not so much. The crux of the matter is
that the code that does this (__page_change_att_set_clr) has only
limited information so when it tries to the change it gets
the "raw" unfiltered information instead of the properly filtered one -
and the "raw" one tell it that PSE bit is on (while infact it
is not).  As a result when the PTE is set to be WB from WC, we get
tons of:

:WARNING: at arch/x86/xen/mmu.c:475 xen_make_pte+0x67/0xa0()
:Hardware name: HP xw4400 Workstation
.. snip..
:Pid: 27, comm: kswapd0 Tainted: G        W    3.2.2-1.fc16.x86_64 #1
:Call Trace:
: [<ffffffff8106dd1f>] warn_slowpath_common+0x7f/0xc0
: [<ffffffff8106dd7a>] warn_slowpath_null+0x1a/0x20
: [<ffffffff81005a17>] xen_make_pte+0x67/0xa0
: [<ffffffff810051bd>] __raw_callee_save_xen_make_pte+0x11/0x1e
: [<ffffffff81040e15>] ? __change_page_attr_set_clr+0x9d5/0xc00
: [<ffffffff8114c2e8>] ? __purge_vmap_area_lazy+0x158/0x1d0
: [<ffffffff8114cca5>] ? vm_unmap_aliases+0x175/0x190
: [<ffffffff81041168>] change_page_attr_set_clr+0x128/0x4c0
: [<ffffffff81041542>] set_pages_array_wb+0x42/0xa0
: [<ffffffff8100a9b2>] ? check_events+0x12/0x20
: [<ffffffffa0074d4c>] ttm_pages_put+0x1c/0x70 [ttm]
: [<ffffffffa0074e98>] ttm_page_pool_free+0xf8/0x180 [ttm]
: [<ffffffffa0074f78>] ttm_pool_mm_shrink+0x58/0x90 [ttm]
: [<ffffffff8112ba04>] shrink_slab+0x154/0x310
: [<ffffffff8112f17a>] balance_pgdat+0x4fa/0x6c0
: [<ffffffff8112f4b8>] kswapd+0x178/0x3d0
: [<ffffffff815df134>] ? __schedule+0x3d4/0x8c0
: [<ffffffff81090410>] ? remove_wait_queue+0x50/0x50
: [<ffffffff8112f340>] ? balance_pgdat+0x6c0/0x6c0
: [<ffffffff8108fb6c>] kthread+0x8c/0xa0

for every page. The proper fix for this is has been posted
and is https://lkml.org/lkml/2012/2/10/228
"x86/cpa: Use pte_attrs instead of pte_flags on CPA/set_p.._wb/wc operations."
along with a detailed description of the problem and solution.

But since that posting has gone nowhere I am proposing
this band-aid solution so that at least users don't get
the page corruption (the pages that are WC don't get changed to WB
and end up being recycled for filesystem or other things causing
mysterious crashes).

The negative impact of this patch is that users of WC flag
(which are InfiniBand, radeon, nouveau drivers) won't be able
to set that flag - so they are going to see performance degradation.
But stability is more important here.

Fixes RH BZ# 742032, 787403, and 745574
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

commit 7347b408 "xen: Allow
unprivileged Xen domains to create iomap pages" added a redundant
line in the early bootup code to filter out the PTE. That
filtering is already done a bit earlier so this extra processing
is not required.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Currently, the NMI handler tests if it is nested by checking the
special variable saved on the stack (set during NMI handling)
and whether the saved stack is the NMI stack as well (to prevent
the race when the variable is set to zero).

But userspace may set their %rsp to any value as long as they do
not derefence it, and it may make it point to the NMI stack,
which will prevent NMIs from triggering while the userspace app
is running. (I tested this, and it is indeed the case)

Add another check to determine nested NMIs by looking at the
saved %cs (code segment register) and making sure that it is the
kernel code segment.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: <stable@kernel.org>
Link: http://lkml.kernel.org/r/1329687817.1561.27.camel@acer.local.homeSigned-off-by: NIngo Molnar <mingo@elte.hu>

After all the FPU state cleanups and finally finding the problem that
caused all our FPU save/restore problems, this re-introduces the
preloading of FPU state that was removed in commit b3b0870e ("i387:
do not preload FPU state at task switch time").

However, instead of simply reverting the removal, this reimplements
preloading with several fixes, most notably

 - properly abstracted as a true FPU state switch, rather than as
   open-coded save and restore with various hacks.

   In particular, implementing it as a proper FPU state switch allows us
   to optimize the CR0.TS flag accesses: there is no reason to set the
   TS bit only to then almost immediately clear it again.  CR0 accesses
   are quite slow and expensive, don't flip the bit back and forth for
   no good reason.

 - Make sure that the same model works for both x86-32 and x86-64, so
   that there are no gratuitous differences between the two due to the
   way they save and restore segment state differently due to
   architectural differences that really don't matter to the FPU state.

 - Avoid exposing the "preload" state to the context switch routines,
   and in particular allow the concept of lazy state restore: if nothing
   else has used the FPU in the meantime, and the process is still on
   the same CPU, we can avoid restoring state from memory entirely, just
   re-expose the state that is still in the FPU unit.

   That optimized lazy restore isn't actually implemented here, but the
   infrastructure is set up for it.  Of course, older CPU's that use
   'fnsave' to save the state cannot take advantage of this, since the
   state saving also trashes the state.

In other words, there is now an actual _design_ to the FPU state saving,
rather than just random historical baggage.  Hopefully it's easier to
follow as a result.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This moves the bit that indicates whether a thread has ownership of the
FPU from the TS_USEDFPU bit in thread_info->status to a word of its own
(called 'has_fpu') in task_struct->thread.has_fpu.

This fixes two independent bugs at the same time:

 - changing 'thread_info->status' from the scheduler causes nasty
   problems for the other users of that variable, since it is defined to
   be thread-synchronous (that's what the "TS_" part of the naming was
   supposed to indicate).

   So perfectly valid code could (and did) do

	ti->status |= TS_RESTORE_SIGMASK;

   and the compiler was free to do that as separate load, or and store
   instructions.  Which can cause problems with preemption, since a task
   switch could happen in between, and change the TS_USEDFPU bit. The
   change to TS_USEDFPU would be overwritten by the final store.

   In practice, this seldom happened, though, because the 'status' field
   was seldom used more than once, so gcc would generally tend to
   generate code that used a read-modify-write instruction and thus
   happened to avoid this problem - RMW instructions are naturally low
   fat and preemption-safe.

 - On x86-32, the current_thread_info() pointer would, during interrupts
   and softirqs, point to a *copy* of the real thread_info, because
   x86-32 uses %esp to calculate the thread_info address, and thus the
   separate irq (and softirq) stacks would cause these kinds of odd
   thread_info copy aliases.

   This is normally not a problem, since interrupts aren't supposed to
   look at thread information anyway (what thread is running at
   interrupt time really isn't very well-defined), but it confused the
   heck out of irq_fpu_usable() and the code that tried to squirrel
   away the FPU state.

   (It also caused untold confusion for us poor kernel developers).

It also turns out that using 'task_struct' is actually much more natural
for most of the call sites that care about the FPU state, since they
tend to work with the task struct for other reasons anyway (ie
scheduling).  And the FPU data that we are going to save/restore is
found there too.

Thanks to Arjan Van De Ven <arjan@linux.intel.com> for pointing us to
the %esp issue.

Cc: Arjan van de Ven <arjan@linux.intel.com>
Reported-and-tested-by: NRaphael Prevost <raphael@buro.asia>
Acked-and-tested-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Tested-by: NPeter Anvin <hpa@zytor.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception is
pending.  In order to not leak FIP state from one process to another, we
need to do a floating point load after the fxsave of the old process,
and before the fxrstor of the new FPU state.  That resets the state to
the (uninteresting) kernel load, rather than some potentially sensitive
user information.

We used to do this directly after the FPU state save, but that is
actually very inconvenient, since it

 (a) corrupts what is potentially perfectly good FPU state that we might
     want to lazy avoid restoring later and

 (b) on x86-64 it resulted in a very annoying ordering constraint, where
     "__unlazy_fpu()" in the task switch needs to be delayed until after
     the DS segment has been reloaded just to get the new DS value.

Coupling it to the fxrstor instead of the fxsave automatically avoids
both of these issues, and also ensures that we only do it when actually
necessary (the FP state after a save may never actually get used).  It's
simply a much more natural place for the leaked state cleanup.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Yes, taking the trap to re-load the FPU/MMX state is expensive, but so
is spending several days looking for a bug in the state save/restore
code.  And the preload code has some rather subtle interactions with
both paravirtualization support and segment state restore, so it's not
nearly as simple as it should be.

Also, now that we no longer necessarily depend on a single bit (ie
TS_USEDFPU) for keeping track of the state of the FPU, we migth be able
to do better.  If we are really switching between two processes that
keep touching the FP state, save/restore is inevitable, but in the case
of having one process that does most of the FPU usage, we may actually
be able to do much better than the preloading.

In particular, we may be able to keep track of which CPU the process ran
on last, and also per CPU keep track of which process' FP state that CPU
has.  For modern CPU's that don't destroy the FPU contents on save time,
that would allow us to do a lazy restore by just re-enabling the
existing FPU state - with no restore cost at all!
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This creates three helper functions that do the TS_USEDFPU accesses, and
makes everybody that used to do it by hand use those helpers instead.

In addition, there's a couple of helper functions for the "change both
CR0.TS and TS_USEDFPU at the same time" case, and the places that do
that together have been changed to use those.  That means that we have
fewer random places that open-code this situation.

The intent is partly to clarify the code without actually changing any
semantics yet (since we clearly still have some hard to reproduce bug in
this area), but also to make it much easier to use another approach
entirely to caching the CR0.TS bit for software accesses.

Right now we use a bit in the thread-info 'status' variable (this patch
does not change that), but we might want to make it a full field of its
own or even make it a per-cpu variable.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Touching TS_USEDFPU without touching CR0.TS is confusing, so don't do
it.  By moving it into the callers, we always do the TS_USEDFPU next to
the CR0.TS accesses in the source code, and it's much easier to see how
the two go hand in hand.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit 5b1cbac3 ("i387: make irq_fpu_usable() tests more robust")
added a sanity check to the #NM handler to verify that we never cause
the "Device Not Available" exception in kernel mode.

However, that check actually pinpointed a (fundamental) race where we do
cause that exception as part of the signal stack FPU state save/restore
code.

Because we use the floating point instructions themselves to save and
restore state directly from user mode, we cannot do that atomically with
testing the TS_USEDFPU bit: the user mode access itself may cause a page
fault, which causes a task switch, which saves and restores the FP/MMX
state from the kernel buffers.

This kind of "recursive" FP state save is fine per se, but it means that
when the signal stack save/restore gets restarted, it will now take the
'#NM' exception we originally tried to avoid.  With preemption this can
happen even without the page fault - but because of the user access, we
cannot just disable preemption around the save/restore instruction.

There are various ways to solve this, including using the
"enable/disable_page_fault()" helpers to not allow page faults at all
during the sequence, and fall back to copying things by hand without the
use of the native FP state save/restore instructions.

However, the simplest thing to do is to just allow the #NM from kernel
space, but fix the race in setting and clearing CR0.TS that this all
exposed: the TS bit changes and the TS_USEDFPU bit absolutely have to be
atomic wrt scheduling, so while the actual state save/restore can be
interrupted and restarted, the act of actually clearing/setting CR0.TS
and the TS_USEDFPU bit together must not.

Instead of just adding random "preempt_disable/enable()" calls to what
is already excessively ugly code, this introduces some helper functions
that mostly mirror the "kernel_fpu_begin/end()" functionality, just for
the user state instead.

Those helper functions should probably eventually replace the other
ad-hoc CR0.TS and TS_USEDFPU tests too, but I'll need to think about it
some more: the task switching functionality in particular needs to
expose the difference between the 'prev' and 'next' threads, while the
new helper functions intentionally were written to only work with
'current'.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The check for save_init_fpu() (introduced in commit 5b1cbac3: "i387:
make irq_fpu_usable() tests more robust") was the wrong way around, but
I hadn't noticed, because my "tests" were bogus: the FPU exceptions are
disabled by default, so even doing a divide by zero never actually
triggers this code at all unless you do extra work to enable them.

So if anybody did enable them, they'd get one spurious warning.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Some code - especially the crypto layer - wants to use the x86
FP/MMX/AVX register set in what may be interrupt (typically softirq)
context.

That *can* be ok, but the tests for when it was ok were somewhat
suspect.  We cannot touch the thread-specific status bits either, so
we'd better check that we're not going to try to save FP state or
anything like that.

Now, it may be that the TS bit is always cleared *before* we set the
USEDFPU bit (and only set when we had already cleared the USEDFP
before), so the TS bit test may actually have been sufficient, but it
certainly was not obviously so.

So this explicitly verifies that we will not touch the TS_USEDFPU bit,
and adds a few related sanity-checks.  Because it seems that somehow
AES-NI is corrupting user FP state.  The cause is not clear, and this
patch doesn't fix it, but while debugging it I really wanted the code to
be more obviously correct and robust.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

It was marked asmlinkage for some really old and stale legacy reasons.
Fix that and the equally stale comment.

Noticed when debugging the irq_fpu_usable() bugs.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

For L1 instruction cache and L2 cache the shared CPU information
is wrong. On current AMD family 15h CPUs those caches are shared
between both cores of a compute unit.

This fixes https://bugzilla.kernel.org/show_bug.cgi?id=42607Signed-off-by: NAndreas Herrmann <andreas.herrmann3@amd.com>
Cc: Petkov Borislav <Borislav.Petkov@amd.com>
Cc: Dave Jones <davej@redhat.com>
Cc: <stable@kernel.org>
Link: http://lkml.kernel.org/r/20120208195229.GA17523@alberich.amd.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

The following patch fixes a bug introduced by the following
commit:

        e050e3f0 ("perf: Fix broken interrupt rate throttling")

The patch caused the following warning to pop up depending on
the sampling frequency adjustments:

  ------------[ cut here ]------------
  WARNING: at arch/x86/kernel/cpu/perf_event.c:995 x86_pmu_start+0x79/0xd4()

It was caused by the following call sequence:

perf_adjust_freq_unthr_context.part() {
     stop()
     if (delta > 0) {
          perf_adjust_period() {
              if (period > 8*...) {
                  stop()
                  ...
                  start()
              }
          }
      }
      start()
}

Which caused a double start and a double stop, thus triggering
the assert in x86_pmu_start().

The patch fixes the problem by avoiding the double calls. We
pass a new argument to perf_adjust_period() to indicate whether
or not the event is already stopped. We can't just remove the
start/stop from that function because it's called from
__perf_event_overflow where the event needs to be reloaded via a
stop/start back-toback call.

The patch reintroduces the assertion in x86_pmu_start() which
was removed by commit:

	84f2b9b2 ("perf: Remove deprecated WARN_ON_ONCE()")

In this second version, we've added calls to disable/enable PMU
during unthrottling or frequency adjustment based on bug report
of spurious NMI interrupts from Eric Dumazet.
Reported-and-tested-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NStephane Eranian <eranian@google.com>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: markus@trippelsdorf.de
Cc: paulus@samba.org
Link: http://lkml.kernel.org/r/20120207133956.GA4932@quad
[ Minor edits to the changelog and to the code ]
Signed-off-by: NIngo Molnar <mingo@elte.hu>

AMD processors will never support /dev/cpu/microcode updating so
just silently fail instead of printing out a warning for every
cpu.
Signed-off-by: NPrarit Bhargava <prarit@redhat.com>
Cc: Borislav Petkov <borislav.petkov@amd.com>
Link: http://lkml.kernel.org/r/1328552935-965-1-git-send-email-prarit@redhat.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

CC: stable@kernel.org #2.6.37 and onwards
Signed-off-by: NStefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

When a user offlines a VCPU and then onlines it, we get:

NMI watchdog disabled (cpu2): hardware events not enabled
BUG: scheduling while atomic: swapper/2/0/0x00000002
Modules linked in: dm_multipath dm_mod xen_evtchn iscsi_boot_sysfs iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi scsi_mod libcrc32c crc32c radeon fbco
 ttm bitblit softcursor drm_kms_helper xen_blkfront xen_netfront xen_fbfront fb_sys_fops sysimgblt sysfillrect syscopyarea xen_kbdfront xenfs [last unloaded:

Pid: 0, comm: swapper/2 Tainted: G           O 3.2.0phase15.1-00003-gd6f7f5b-dirty #4
Call Trace:
 [<ffffffff81070571>] __schedule_bug+0x61/0x70
 [<ffffffff8158eb78>] __schedule+0x798/0x850
 [<ffffffff8158ed6a>] schedule+0x3a/0x50
 [<ffffffff810349be>] cpu_idle+0xbe/0xe0
 [<ffffffff81583599>] cpu_bringup_and_idle+0xe/0x10

The reason for this should be obvious from this call-chain:
cpu_bringup_and_idle:
 \- cpu_bringup
  |   \-[preempt_disable]
  |
  |- cpu_idle
       \- play_dead [assuming the user offlined the VCPU]
       |     \
       |     +- (xen_play_dead)
       |          \- HYPERVISOR_VCPU_off [so VCPU is dead, once user
       |          |                       onlines it starts from here]
       |          \- cpu_bringup [preempt_disable]
       |
       +- preempt_enable_no_reschedule()
       +- schedule()
       \- preempt_enable()

So we have two preempt_disble() and one preempt_enable(). Calling
preempt_enable() after the cpu_bringup() in the xen_play_dead
fixes the imbalance.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

With the new throttling/unthrottling code introduced with
commit:

  e050e3f0 ("perf: Fix broken interrupt rate throttling")

we occasionally hit two WARN_ON_ONCE() checks in:

  - intel_pmu_pebs_enable()
  - intel_pmu_lbr_enable()
  - x86_pmu_start()

The assertions are no longer problematic. There is a valid
path where they can trigger but it is harmless.

The assertion can be triggered with:

  $ perf record -e instructions:pp ....

Leading to paths:

  intel_pmu_pebs_enable
  intel_pmu_enable_event
  x86_perf_event_set_period
  x86_pmu_start
  perf_adjust_freq_unthr_context
  perf_event_task_tick
  scheduler_tick

And:

  intel_pmu_lbr_enable
  intel_pmu_enable_event
  x86_perf_event_set_period
  x86_pmu_start
  perf_adjust_freq_unthr_context.
  perf_event_task_tick
  scheduler_tick

cpuc->enabled is always on because when we get to
perf_adjust_freq_unthr_context() the PMU is not totally
disabled. Furthermore when we need to adjust a period,
we only stop the event we need to change and not the
entire PMU. Thus, when we re-enable, cpuc->enabled is
already set. Note that when we stop the event, both
pebs and lbr are stopped if necessary (and possible).
Signed-off-by: NStephane Eranian <eranian@google.com>
Cc: peterz@infradead.org
Link: http://lkml.kernel.org/r/20120202110401.GA30911@quadSigned-off-by: NIngo Molnar <mingo@elte.hu>

Return to behaviour perf MSR had before introducing vPMU in case vPMU
is disabled. Some guests access those registers unconditionally and do
not expect it to fail.
Signed-off-by: NGleb Natapov <gleb@redhat.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

On hosts without this patch, 32bit guests will crash (and 64bit guests
may behave in a wrong way) for example by simply executing following
nasm-demo-application:

    [bits 32]
    global _start
    SECTION .text
    _start: syscall

(I tested it with winxp and linux - both always crashed)

    Disassembly of section .text:

    00000000 <_start>:
       0:   0f 05                   syscall

The reason seems a missing "invalid opcode"-trap (int6) for the
syscall opcode "0f05", which is not available on Intel CPUs
within non-longmodes, as also on some AMD CPUs within legacy-mode.
(depending on CPU vendor, MSR_EFER and cpuid)

Because previous mentioned OSs may not engage corresponding
syscall target-registers (STAR, LSTAR, CSTAR), they remain
NULL and (non trapping) syscalls are leading to multiple
faults and finally crashs.

Depending on the architecture (AMD or Intel) pretended by
guests, various checks according to vendor's documentation
are implemented to overcome the current issue and behave
like the CPUs physical counterparts.

[mtosatti: cleanup/beautify code]
Signed-off-by: NStephan Baerwolf <stephan.baerwolf@tu-ilmenau.de>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

In order to be able to proceed checks on CPU-specific properties
within the emulator, function "get_cpuid" is introduced.
With "get_cpuid" it is possible to virtually call the guests
"cpuid"-opcode without changing the VM's context.

[mtosatti: cleanup/beautify code]
Signed-off-by: NStephan Baerwolf <stephan.baerwolf@tu-ilmenau.de>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>

This commit removes the reboot quirk originally added by commit
e19e074b ("x86: Fix reboot problem on VersaLogic Menlow boards").

Testing with a VersaLogic Ocelot (VL-EPMs-21a rev 1.00 w/ BIOS
6.5.102) revealed the following regarding the reboot hang
problem:

- v2.6.37 reboot=bios was needed.

- v2.6.38-rc1: behavior changed, reboot=acpi is needed,
  reboot=kbd and reboot=bios results in system hang.

- v2.6.38: VersaLogic patch (e19e074b "x86: Fix reboot problem on
  VersaLogic Menlow boards") was applied prior to v2.6.38-rc7.  This
  patch sets a quirk for VersaLogic Menlow boards that forces the use
  of reboot=bios, which doesn't work anymore.

- v3.2: It seems that commit 660e34ce ("x86: Reorder reboot method
  preferences") changed the default reboot method to acpi prior to
  v3.0-rc1, which means the default behavior is appropriate for the
  Ocelot.  No VersaLogic quirk is required.

The Ocelot board used for testing can successfully reboot w/out
having to pass any reboot= arguments for all 3 current versions
of the BIOS.
Signed-off-by: NMichael D Labriola <michael.d.labriola@gmail.com>
Cc: Matthew Garrett <mjg@redhat.com>
Cc: Michael D Labriola <mlabriol@gdeb.com>
Cc: Kushal Koolwal <kushalkoolwal@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/87vcnub9hu.fsf@gmail.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

Skip DMI checks for vendor specific reboot quirks if the user
passed in a reboot= arg on the command line - we should never
override user choices.
Signed-off-by: NMichael D Labriola <michael.d.labriola@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Michael D Labriola <mlabriol@gdeb.com>
Cc: Matthew Garrett <mjg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/87wr8ab9od.fsf@gmail.comSigned-off-by: NIngo Molnar <mingo@elte.hu>