KVM: nSVM: Simplify error handling of nested_svm_copy_vmcb12_to_cache()

nested_svm_vmrun() currently stores the return value of
nested_svm_copy_vmcb12_to_cache() in a local variable 'err', separate
from the generally used 'ret' variable. This is done to have a single
call to kvm_skip_emulated_instruction(), such that we can store the
return value of kvm_skip_emulated_instruction() in 'ret', and then
re-check the return value of nested_svm_copy_vmcb12_to_cache() in 'err'.

The code is unnecessarily confusing. Instead, call
kvm_skip_emulated_instruction() in the failure path of
nested_svm_copy_vmcb12_to_cache() if the return value is not -EFAULT,
and drop 'err'.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260306210900.1933788-3-yosry@kernel.org
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 b191c6cab57dbcaeb3ffcd878d09390481418e41..3ffde1ff719bde601ab10e8d69e31dc30b43b9eb 100644 (file)
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1079,7 +1079,7 @@ static int nested_svm_copy_vmcb12_to_cache(struct kvm_vcpu *vcpu, u64 vmcb12_gpa
 int nested_svm_vmrun(struct kvm_vcpu *vcpu)
 {
        struct vcpu_svm *svm = to_svm(vcpu);
-       int ret, err;
+       int ret;
        u64 vmcb12_gpa;
        struct vmcb *vmcb01 = svm->vmcb01.ptr;
 
@@ -1104,19 +1104,20 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
                return -EINVAL;
 
        vmcb12_gpa = svm->vmcb->save.rax;
-       err = nested_svm_copy_vmcb12_to_cache(vcpu, vmcb12_gpa);
-       if (err == -EFAULT) {
-               kvm_inject_gp(vcpu, 0);
-               return 1;
+
+       ret = nested_svm_copy_vmcb12_to_cache(vcpu, vmcb12_gpa);
+       if (ret) {
+               if (ret == -EFAULT) {
+                       kvm_inject_gp(vcpu, 0);
+                       return 1;
+               }
+
+               /* Advance RIP past VMRUN as part of the nested #VMEXIT. */
+               return kvm_skip_emulated_instruction(vcpu);
        }
 
-       /*
-        * Advance RIP if #GP or #UD are not injected, but otherwise stop if
-        * copying and checking vmcb12 failed.
-        */
+       /* At this point, VMRUN is guaranteed to not fault; advance RIP. */
        ret = kvm_skip_emulated_instruction(vcpu);
-       if (err)
-               return ret;
 
        /*
         * Since vmcb01 is not in use, we can use it to store some of the L1