Re: [PATCH 0/5] Introduce a quirk to control memslot zap behavior

[Edgecombe, Rick P]

On Thu, 2024-06-13 at 14:06 +0800, Yan Zhao wrote:
>       a) Add a condition for TDX VM type in kvm_arch_flush_shadow_memslot()
>          besides the testing of kvm_check_has_quirk(). It is similar to
>          "all new VM types have the quirk disabled". e.g.
> 
>          static inline bool kvm_memslot_flush_zap_all(struct kvm
> *kvm)                    
>         
> {                                                                             
>    
>               return kvm->arch.vm_type != KVM_X86_TDX_VM
> &&                               
>                      kvm_check_has_quirk(kvm,
> KVM_X86_QUIRK_SLOT_ZAP_ALL);                
>          }
>          
>       b) Init the disabled_quirks based on VM type in kernel, extend
>          disabled_quirk querying/setting interface to enforce the quirk to
>          be disabled for TDX.

I'd prefer to go with option (a) here. Because we don't have any behavior
defined yet for KVM_X86_TDX_VM, we don't really need to "disable a quirk" of it.

Instead we could just define KVM_X86_QUIRK_SLOT_ZAP_ALL to be about the behavior
of the existing vm_types. It would be a few lines of documentation to save
implementing and maintaining a whole interface with special logic for TDX. So to
me it doesn't seem worth it, unless there is some other user for a new more
complex quirk interface.