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

[Paolo Bonzini]

On 11/9/22 16:20, Sean Christopherson wrote:
> > 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.

I tried to avoid the "in the future" phrasing which some people dislike. 
 I'll rephrase anyway.  Even without taking 
RDMSR/WRMSR/VMLOAD/VMRUN/VMSAVE into account, avoiding the potential 
clash with 32-bit register arguments is a decent reason for the patch 
anyway.

Paolo