kvm: x86: Propagate guest PCIDs to host PCIDs

When using shadow paging mode, propagate the guest's PCID value to
the shadow CR3 in the host instead of always using PCID 0.

Signed-off-by: Junaid Shahid <junaids@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu.h

@@ -86,10 +86,25 @@ static inline int kvm_mmu_reload(struct kvm_vcpu *vcpu)
 	return kvm_mmu_load(vcpu);
 }
 
+static inline unsigned long kvm_get_pcid(struct kvm_vcpu *vcpu, gpa_t cr3)
+{
+	BUILD_BUG_ON((X86_CR3_PCID_MASK & PAGE_MASK) != 0);
+
+	return kvm_read_cr4_bits(vcpu, X86_CR4_PCIDE)
+	       ? cr3 & X86_CR3_PCID_MASK
+	       : 0;
+}
+
+static inline unsigned long kvm_get_active_pcid(struct kvm_vcpu *vcpu)
+{
+	return kvm_get_pcid(vcpu, kvm_read_cr3(vcpu));
+}
+
 static inline void kvm_mmu_load_cr3(struct kvm_vcpu *vcpu)
 {
 	if (VALID_PAGE(vcpu->arch.mmu.root_hpa))
-		vcpu->arch.mmu.set_cr3(vcpu, vcpu->arch.mmu.root_hpa);
+		vcpu->arch.mmu.set_cr3(vcpu, vcpu->arch.mmu.root_hpa |
+					     kvm_get_active_pcid(vcpu));
 }
 
 /*