Revision - c4d2188 - KVM: x86: Update cpuid properly when CR4.OSXAVE or CR4.PKE is changed - origin: https://github.com/torvalds/linux

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05 April 2024, 19:05:47 UTC

Revision c4d2188206bafa177ea58e9a25b952baa0bf7712 authored by Wei Huang on 01 May 2018, 14:49:54 UTC, committed by Radim Krčmář on 24 May 2018, 15:57:18 UTC

KVM: x86: Update cpuid properly when CR4.OSXAVE or CR4.PKE is changed

The CPUID bits of OSXSAVE (function=0x1) and OSPKE (func=0x7, leaf=0x0)
allows user apps to detect if OS has set CR4.OSXSAVE or CR4.PKE. KVM is
supposed to update these CPUID bits when CR4 is updated. Current KVM
code doesn't handle some special cases when updates come from emulator.
Here is one example:

  Step 1: guest boots
  Step 2: guest OS enables XSAVE ==> CR4.OSXSAVE=1 and CPUID.OSXSAVE=1
  Step 3: guest hot reboot ==> QEMU reset CR4 to 0, but CPUID.OSXAVE==1
  Step 4: guest os checks CPUID.OSXAVE, detects 1, then executes xgetbv

Step 4 above will cause an #UD and guest crash because guest OS hasn't
turned on OSXAVE yet. This patch solves the problem by comparing the the
old_cr4 with cr4. If the related bits have been changed,
kvm_update_cpuid() needs to be called.

Signed-off-by: Wei Huang <wei@redhat.com>
Reviewed-by: Bandan Das <bsd@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

1 parent d8f2f49

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Tip revision: c4d2188206bafa177ea58e9a25b952baa0bf7712 authored by Wei Huang on 01 May 2018, 14:49:54 UTC
KVM: x86: Update cpuid properly when CR4.OSXAVE or CR4.PKE is changed

Tip revision: c4d2188

File	Mode	Size
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arch
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certs
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drivers
firmware
fs
include
init
ipc
kernel
lib
mm
net
samples
scripts
security
sound
tools
usr
virt
.clang-format	-rw-r--r--	12.8 KB
.cocciconfig	-rw-r--r--	59 bytes
.get_maintainer.ignore	-rw-r--r--	31 bytes
.gitattributes	-rw-r--r--	30 bytes
.gitignore	-rw-r--r--	1.5 KB
.mailmap	-rw-r--r--	9.2 KB
COPYING	-rw-r--r--	423 bytes
CREDITS	-rw-r--r--	96.3 KB
Kbuild	-rw-r--r--	2.2 KB
Kconfig	-rw-r--r--	287 bytes
MAINTAINERS	-rw-r--r--	441.9 KB
Makefile	-rw-r--r--	61.0 KB
README	-rw-r--r--	800 bytes

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KVM: x86: Update cpuid properly when CR4.OSXAVE or CR4.PKE is changed

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