Re: [PATCH 03/11] KVM: SVM: adjust register allocation for __svm_vcpu_run

[Sean Christopherson]

On Wed, Nov 09, 2022, Paolo Bonzini wrote:
> In preparation for moving vmload/vmsave to __svm_vcpu_run,

__svm_vcpu_run()

> keep the pointer to the struct vcpu_svm in %rdi.  This way
> it is possible to load svm->vmcb01.pa in %rax without
> clobbering the pointer to svm itself.

If you feel like doing fixup before pushing, add a note to call out that avoiding
RAX will also be "necessary" to play nice with loading/storing MSR_SPEC_CTRL?
When fiddling with this code, I found the RDMSR/WRMSR clobbers to be far more
problematic than the VMCB pointers.

> No functional change intended.
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: a149180fbcf3 ("x86: Add magic AMD return-thunk")
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>

Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx>