KVM: nSVM: Use kvm_rax_read() now that it's mode-aware

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>
Link: https://patch.msgid.link/20260529222223.870923-11-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index be76718802618b6f0799455d9d54d966c9afe6aa..de9de9cc9d692c26efbac8a641226fe2b9484f31 100644 (file)
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1135,7 +1135,7 @@ 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 ee8f6664f6f3eed9656de42a472e5f5f62adf29d..f8ab5bae368ccda86649f5a9f31aefd0c5a6cfe2 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2206,7 +2206,7 @@ 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;
@@ -2314,7 +2314,7 @@ 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;
 
                /*