[PATCH v2 10/15] KVM: nSVM: Use kvm_rax_read() now that it's mode-aware

[Sean Christopherson <seanjc@google.com>]

Now that kvm_rax_read() truncates the output value to 32 bits if the
vCPU isn't in 64-bit mode, use it instead of the more verbose (and very
technically slower) kvm_register_read().

Note!  VMLOAD, VMSAVE, and VMRUN emulation are still technically buggy,
as they can use EAX (versus RAX) in 64-bit mode via an operand size
prefix.  Don't bother trying to handle that case, as it would require
decoding the code stream, which would open an entirely different can of
worms, and in practice no sane guest would shove garbage into RAX[63:32]
and then execute VMLOAD/VMSAVE/VMRUN with just EAX.

No functional change intended.

Cc: Yosry Ahmed <yosry@kernel.org>
Reviewed-by: Yosry Ahmed <yosry@kernel.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/svm/nested.c | 2 +-
 arch/x86/kvm/svm/svm.c    | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 7b2d804ef2b0..4b1259eecec5 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1119,7 +1119,7 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
 	if (WARN_ON_ONCE(!svm->nested.initialized))
 		return -EINVAL;
 
-	vmcb12_gpa = kvm_register_read(vcpu, VCPU_REGS_RAX);
+	vmcb12_gpa = kvm_rax_read(vcpu);
 	if (!page_address_valid(vcpu, vmcb12_gpa)) {
 		kvm_inject_gp(vcpu, 0);
 		return 1;
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 02fb9560c26e..6379c389d811 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2217,7 +2217,7 @@ static int intr_interception(struct kvm_vcpu *vcpu)
 
 static int vmload_vmsave_interception(struct kvm_vcpu *vcpu, bool vmload)
 {
-	u64 vmcb12_gpa = kvm_register_read(vcpu, VCPU_REGS_RAX);
+	u64 vmcb12_gpa = kvm_rax_read(vcpu);
 	struct vcpu_svm *svm = to_svm(vcpu);
 	struct vmcb *vmcb12;
 	struct kvm_host_map map;
@@ -2325,7 +2325,7 @@ static int gp_interception(struct kvm_vcpu *vcpu)
 		if (nested_svm_check_permissions(vcpu))
 			return 1;
 
-		if (!page_address_valid(vcpu, kvm_register_read(vcpu, VCPU_REGS_RAX)))
+		if (!page_address_valid(vcpu, kvm_rax_read(vcpu)))
 			goto reinject;
 
 		/*
-- 
2.54.0.563.g4f69b47b94-goog