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authorJoerg Roedel <jroedel@suse.de>2019-02-21 14:52:13 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-02-23 09:05:14 +0100
commit49e1a9d1169adcffee99967130ff6d3b79d5fbe6 (patch)
treee0bc0dc5b053e99c97acbe56ae0c6c7a73a908dc
parent94801fd5ab2352830a86ca59b1e6377e35b6a074 (diff)
KVM: VMX: Fix x2apic check in vmx_msr_bitmap_mode()
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>
-rw-r--r--arch/x86/kvm/vmx.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index aee2886a387c..14553f6c03a6 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -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;