linux-stable.git/arch/x86/kernel/fpu/init.c, branch linux-4.9.y

x86/fpu: Hard-disable lazy FPU mode

2018-06-16T07:52:32+00:00

commit ca6938a1cd8a1c5e861a99b67f84ac166fc2b9e7 upstream.

Since commit:

  58122bf1d856 ("x86/fpu: Default eagerfpu=on on all CPUs")

... in Linux 4.6, eager FPU mode has been the default on all x86
systems, and no one has reported any regressions.

This patch removes the ability to enable lazy mode: use_eager_fpu()
becomes "return true" and all of the FPU mode selection machinery is
removed.

Signed-off-by: Andy Lutomirski 
Signed-off-by: Rik van Riel 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Dave Hansen 
Cc: Denys Vlasenko 
Cc: Fenghua Yu 
Cc: H. Peter Anvin 
Cc: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Peter Zijlstra 
Cc: Quentin Casasnovas 
Cc: Thomas Gleixner 
Cc: pbonzini@redhat.com
Link: http://lkml.kernel.org/r/1475627678-20788-3-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

KVM: x86: Fix load damaged SSEx MXCSR register

2017-05-25T13:44:34+00:00

commit a575813bfe4bc15aba511a5e91e61d242bff8b9d upstream.

Reported by syzkaller:

   BUG: unable to handle kernel paging request at ffffffffc07f6a2e
   IP: report_bug+0x94/0x120
   PGD 348e12067
   P4D 348e12067
   PUD 348e14067
   PMD 3cbd84067
   PTE 80000003f7e87161

   Oops: 0003 [#1] SMP
   CPU: 2 PID: 7091 Comm: kvm_load_guest_ Tainted: G           OE   4.11.0+ #8
   task: ffff92fdfb525400 task.stack: ffffbda6c3d04000
   RIP: 0010:report_bug+0x94/0x120
   RSP: 0018:ffffbda6c3d07b20 EFLAGS: 00010202
    do_trap+0x156/0x170
    do_error_trap+0xa3/0x170
    ? kvm_load_guest_fpu.part.175+0x12a/0x170 [kvm]
    ? mark_held_locks+0x79/0xa0
    ? retint_kernel+0x10/0x10
    ? trace_hardirqs_off_thunk+0x1a/0x1c
    do_invalid_op+0x20/0x30
    invalid_op+0x1e/0x30
   RIP: 0010:kvm_load_guest_fpu.part.175+0x12a/0x170 [kvm]
    ? kvm_load_guest_fpu.part.175+0x1c/0x170 [kvm]
    kvm_arch_vcpu_ioctl_run+0xed6/0x1b70 [kvm]
    kvm_vcpu_ioctl+0x384/0x780 [kvm]
    ? kvm_vcpu_ioctl+0x384/0x780 [kvm]
    ? sched_clock+0x13/0x20
    ? __do_page_fault+0x2a0/0x550
    do_vfs_ioctl+0xa4/0x700
    ? up_read+0x1f/0x40
    ? __do_page_fault+0x2a0/0x550
    SyS_ioctl+0x79/0x90
    entry_SYSCALL_64_fastpath+0x23/0xc2

SDM mentioned that "The MXCSR has several reserved bits, and attempting to write
a 1 to any of these bits will cause a general-protection exception(#GP) to be
generated". The syzkaller forks' testcase overrides xsave area w/ random values
and steps on the reserved bits of MXCSR register. The damaged MXCSR register
values of guest will be restored to SSEx MXCSR register before vmentry. This
patch fixes it by catching userspace override MXCSR register reserved bits w/
random values and bails out immediately.

Reported-by: Andrey Konovalov 
Reviewed-by: Paolo Bonzini 
Cc: Paolo Bonzini 
Cc: Radim Krčmář 
Signed-off-by: Wanpeng Li 
Signed-off-by: Radim Krčmář 
Signed-off-by: Greg Kroah-Hartman

x86/asm: Move the thread_info::status field to thread_struct

2016-09-15T06:25:12+00:00

Because sched.h and thread_info.h are a tangled mess, I turned
in_compat_syscall() into a macro.  If we had current_thread_struct()
or similar and we could use it from thread_info.h, then this would
be a bit cleaner.

Signed-off-by: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Jann Horn 
Cc: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/ccc8a1b2f41f9c264a41f771bb4a6539a642ad72.1473801993.git.luto@kernel.org
Signed-off-by: Ingo Molnar

x86/fpu/xstate: Re-enable XSAVES

2016-07-11T14:44:01+00:00

We did not handle XSAVES instructions correctly. There were issues in
converting between standard and compacted format when interfacing with
user-space. These issues have been corrected.

Add a WARN_ONCE() to make it clear that XSAVES supervisor states are not
yet implemented.

Signed-off-by: Yu-cheng Yu 
Signed-off-by: Fenghua Yu 
Reviewed-by: Dave Hansen 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Ravi V Shankar 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1468253937-40008-5-git-send-email-fenghua.yu@intel.com
Signed-off-by: Ingo Molnar

x86/fpu/xstate: Rename 'xstate_size' to 'fpu_kernel_xstate_size', to distinguish it from 'fpu_user_xstate_size'

2016-06-18T08:10:18+00:00

User space uses standard format xsave area. fpstate in signal frame
should have standard format size.

To explicitly distinguish between xstate size in kernel space and the
one in user space, we rename 'xstate_size' to 'fpu_kernel_xstate_size'.

Cleanup only, no change in functionality.

Signed-off-by: Fenghua Yu 
[ Rebased the patch and cleaned up the naming. ]
Signed-off-by: Yu-cheng Yu 
Reviewed-by: Dave Hansen 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Dave Hansen 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Peter Zijlstra 
Cc: Quentin Casasnovas 
Cc: Ravi V. Shankar 
Cc: Sai Praneeth Prakhya 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/2ecbae347a5152d94be52adf7d0f3b7305d90d99.1463760376.git.yu-cheng.yu@intel.com
Signed-off-by: Ingo Molnar

x86/fpu/xstate: Define and use 'fpu_user_xstate_size'

2016-06-18T08:10:18+00:00

The kernel xstate area can be in standard or compacted format;
it is always in standard format for user mode. When XSAVES is
enabled, the kernel uses the compacted format and it is necessary
to use a separate fpu_user_xstate_size for signal/ptrace frames.

Signed-off-by: Fenghua Yu 
[ Rebased the patch and cleaned up the naming. ]
Signed-off-by: Yu-cheng Yu 
Reviewed-by: Dave Hansen 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Dave Hansen 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Peter Zijlstra 
Cc: Quentin Casasnovas 
Cc: Ravi V. Shankar 
Cc: Sai Praneeth Prakhya 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/8756ec34dabddfc727cda5743195eb81e8caf91c.1463760376.git.yu-cheng.yu@intel.com
Signed-off-by: Ingo Molnar

x86/cpufeature: Replace cpu_has_fxsr with boot_cpu_has() usage

2016-04-13T09:37:41+00:00

Signed-off-by: Borislav Petkov 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1459801503-15600-9-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar

x86/cpufeature: Replace cpu_has_fpu with boot_cpu_has() usage

2016-04-13T09:37:40+00:00

Use static_cpu_has() in the timing-sensitive paths in fpstate_init() and
fpu__copy().

While at it, simplify the use in init_cyrix() and get rid of the ternary
operator.

Signed-off-by: Borislav Petkov 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1459801503-15600-6-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar

x86/cpufeature: Replace cpu_has_xmm with boot_cpu_has() usage

2016-04-13T09:37:40+00:00

Signed-off-by: Borislav Petkov 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1459801503-15600-5-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar

Merge branch 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2016-03-15T17:23:56+00:00

Pull x86 fpu updates from Ingo Molnar:
 "The biggest change in terms of impact is the changing of the FPU
  context switch model to 'eagerfpu' for all CPU types, via: commit
  58122bf1d856: "x86/fpu: Default eagerfpu=on on all CPUs"

  This makes all FPU saves and restores synchronous and makes the FPU
  code a lot more obvious to read.  In the next cycle, if this change is
  problem free, we'll remove the old lazy FPU restore code altogether.

  This change flushed out some old bugs, which should all be fixed by
  now, BYMMV"

* 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/fpu: Default eagerfpu=on on all CPUs
  x86/fpu: Speed up lazy FPU restores slightly
  x86/fpu: Fold fpu_copy() into fpu__copy()
  x86/fpu: Fix FNSAVE usage in eagerfpu mode
  x86/fpu: Fix math emulation in eager fpu mode