KVM: x86: introduce is_pae_paging

[ Upstream commit bf03d4f9 ]

Checking for 32-bit PAE is quite common around code that fiddles with
the PDPTRs.  Add a function to compress all checks into a single
invocation.

Moving to the common helper also fixes a subtle bug in kvm_set_cr3()
where it fails to check is_long_mode() and results in KVM incorrectly
attempting to load PDPTRs for a 64-bit guest.
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[sean: backport to 4.x; handle vmx.c split in 5.x, call out the bugfix]
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

arch/x86/kvm/vmx.c

@@ -5173,7 +5173,7 @@ static void ept_load_pdptrs(struct kvm_vcpu *vcpu)
 		      (unsigned long *)&vcpu->arch.regs_dirty))
 		return;
 
-	if (is_paging(vcpu) && is_pae(vcpu) && !is_long_mode(vcpu)) {
+	if (is_pae_paging(vcpu)) {
 		vmcs_write64(GUEST_PDPTR0, mmu->pdptrs[0]);
 		vmcs_write64(GUEST_PDPTR1, mmu->pdptrs[1]);
 		vmcs_write64(GUEST_PDPTR2, mmu->pdptrs[2]);
@@ -5185,7 +5185,7 @@ static void ept_save_pdptrs(struct kvm_vcpu *vcpu)
 {
 	struct kvm_mmu *mmu = vcpu->arch.walk_mmu;
 
-	if (is_paging(vcpu) && is_pae(vcpu) && !is_long_mode(vcpu)) {
+	if (is_pae_paging(vcpu)) {
 		mmu->pdptrs[0] = vmcs_read64(GUEST_PDPTR0);
 		mmu->pdptrs[1] = vmcs_read64(GUEST_PDPTR1);
 		mmu->pdptrs[2] = vmcs_read64(GUEST_PDPTR2);
@@ -12013,8 +12013,7 @@ static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool ne
 		 * If PAE paging and EPT are both on, CR3 is not used by the CPU and
 		 * must not be dereferenced.
 		 */
-		if (!is_long_mode(vcpu) && is_pae(vcpu) && is_paging(vcpu) &&
-		    !nested_ept) {
+		if (is_pae_paging(vcpu) && !nested_ept) {
 			if (!load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3)) {
 				*entry_failure_code = ENTRY_FAIL_PDPTE;
 				return 1;

arch/x86/kvm/x86.c

@@ -634,7 +634,7 @@ bool pdptrs_changed(struct kvm_vcpu *vcpu)
 	gfn_t gfn;
 	int r;
 
-	if (is_long_mode(vcpu) || !is_pae(vcpu) || !is_paging(vcpu))
+	if (!is_pae_paging(vcpu))
 		return false;
 
 	if (!test_bit(VCPU_EXREG_PDPTR,
@@ -885,7 +885,7 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
 	if (is_long_mode(vcpu) &&
 	    (cr3 & rsvd_bits(cpuid_maxphyaddr(vcpu), 63)))
 		return 1;
-	else if (is_pae(vcpu) && is_paging(vcpu) &&
+	else if (is_pae_paging(vcpu) &&
 		 !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))
 		return 1;
 
@@ -8348,7 +8348,7 @@ static int __set_sregs(struct kvm_vcpu *vcpu, struct kvm_sregs *sregs)
 		kvm_update_cpuid(vcpu);
 
 	idx = srcu_read_lock(&vcpu->kvm->srcu);
-	if (!is_long_mode(vcpu) && is_pae(vcpu) && is_paging(vcpu)) {
+	if (is_pae_paging(vcpu)) {
 		load_pdptrs(vcpu, vcpu->arch.walk_mmu, kvm_read_cr3(vcpu));
 		mmu_reset_needed = 1;
 	}

arch/x86/kvm/x86.h

@@ -139,6 +139,11 @@ static inline int is_paging(struct kvm_vcpu *vcpu)
 	return likely(kvm_read_cr0_bits(vcpu, X86_CR0_PG));
 }
 
+static inline bool is_pae_paging(struct kvm_vcpu *vcpu)
+{
+	return !is_long_mode(vcpu) && is_pae(vcpu) && is_paging(vcpu);
+}
+
 static inline u32 bit(int bitno)
 {
 	return 1 << (bitno & 31);