9 Nov
2022
9 Nov
'22
4:04 p.m.
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