evie/android_kernel_oneplus_msm8998
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

KVM: VMX: Fix x2apic check in vmx_msr_bitmap_mode()

Browse source 
The stable backport of upstream commit

	904e14fb7cb96 KVM: VMX: make MSR bitmaps per-VCPU

has a bug in vmx_msr_bitmap_mode(). It enables the x2apic
MSR-bitmap when the kernel emulates x2apic for the guest in
software. The upstream version of the commit checkes whether
the hardware has virtualization enabled for x2apic
emulation.

Since KVM emulates x2apic for guests even when the host does
not support x2apic in hardware, this causes the intercept of
at least the X2APIC_TASKPRI MSR to be disabled on machines
not supporting that MSR. The result is undefined behavior,
on some machines (Intel Westmere based) it causes a crash of
the guest kernel when it tries to access that MSR.

Change the check in vmx_msr_bitmap_mode() to match the upstream
code. This fixes the guest crashes observed with stable
kernels starting with v4.4.168 through v4.4.175.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Joerg Roedel 2019-02-21 14:52:13 +01:00 • committed by Greg Kroah-Hartman
parent 94801fd5ab
commit 49e1a9d116
1 changed files with 3 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
arch/x86/kvm/vmx.c
View file

@ -4628,7 +4628,9 @@ static u8 vmx_msr_bitmap_mode(struct kvm_vcpu *vcpu)
{
u8 mode = 0;
if (irqchip_in_kernel(vcpu->kvm) && apic_x2apic_mode(vcpu->arch.apic)) {
if (cpu_has_secondary_exec_ctrls() &&
(vmcs_read32(SECONDARY_VM_EXEC_CONTROL) &
SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE)) {
mode |= MSR_BITMAP_MODE_X2APIC;
if (enable_apicv)
mode |= MSR_BITMAP_MODE_X2APIC_APICV;