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Subject[PATCH 2/2] KVM: X86: Fix loss of CR3_PCID_INVD bit when guest writes CR3
Date
From: Wanpeng Li <wanpengli@tencent.com>

SDM volume 3, section 4.10.4:

* MOV to CR3. The behavior of the instruction depends on the value of CR4.PCIDE:
— If CR4.PCIDE = 1 and bit 63 of the instruction’s source operand is 1, the
instruction is not required to invalidate any TLB entries or entries in
paging-structure caches.

The CR3_PCID_INVD bit should not be removed if CR4.PCIDE = 1 when guest writes
CR3, this patch fixes it.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Junaid Shahid <junaids@google.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
arch/x86/kvm/x86.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9a90668..438f140 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -849,11 +849,13 @@ EXPORT_SYMBOL_GPL(kvm_set_cr4);

int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
{
+ unsigned long cr3_check = cr3;
+
#ifdef CONFIG_X86_64
bool pcid_enabled = kvm_read_cr4_bits(vcpu, X86_CR4_PCIDE);

if (pcid_enabled)
- cr3 &= ~CR3_PCID_INVD;
+ cr3_check &= ~CR3_PCID_INVD;
#endif

if (cr3 == kvm_read_cr3(vcpu) && !pdptrs_changed(vcpu)) {
@@ -863,7 +865,7 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
}

if (is_long_mode(vcpu) &&
- (cr3 & rsvd_bits(cpuid_maxphyaddr(vcpu), 63)))
+ (cr3_check & rsvd_bits(cpuid_maxphyaddr(vcpu), 63)))
return 1;
else if (is_pae(vcpu) && is_paging(vcpu) &&
!load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))
--
2.7.4
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