Re: [RFC PATCH 3/3] nSVM: use svm->nested.save to load vmcb12 registers and avoid TOC/TOU races

[Emanuele Giuseppe Esposito <eesposit@redhat.com>]

On 12/09/2021 12:42, Maxim Levitsky wrote:
>>   
>> -	if (!nested_vmcb_valid_sregs(vcpu, &vmcb12->save) ||
>> +	if (!nested_vmcb_valid_sregs(vcpu, &svm->nested.save) ||
>>   	    !nested_vmcb_check_controls(vcpu, &svm->nested.ctl)) {

> If you use a different struct for the copied fields, then it makes
> sense IMHO to drop the 'control' parameter from nested_vmcb_check_controls,
> and just use the svm->nested.save there directly.
> 

Ok, what you say in patch 2 makes sense to me. I can create a new struct 
vmcb_save_area_cached, but I need to keep nested.ctl because 1) it is 
used also elsewhere, and different fields from the one checked here are 
read/set and 2) using another structure (or the same 
vmcb_save_area_cached) in its place would just duplicate the same fields 
of nested.ctl, creating even more confusion and possible inconsistency.

Let me know if you disagree.

Thank you,
Emanuele