Re: [RFC PATCH v5 037/104] KVM: x86/mmu: Allow non-zero init value for shadow PTE

[Paolo Bonzini]

On 3/4/22 20:48, isaku.yamahata@xxxxxxxxx wrote:
>   static void mmu_spte_clear_no_track(u64 *sptep)
>   {
> -	__update_clear_spte_fast(sptep, 0ull);
> +	__update_clear_spte_fast(sptep, shadow_init_value);
>   }
>   

Please WARN_ON_ONCE if shadow_init_value is nonzero, and then keep 0ull 
as the argument.

I have not thought much of the steps that are needed if were to flip 
both bit 0 and bit 63, so let's at least document that with a WARN.

Otherwise,

Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>

Paolo