Re: [RFC 17/33] KVM: x86/mmu: Allow setting memory attributes if VSM enabled

[Maxim Levitsky <mlevitsk@redhat.com>]

On Wed, 2023-11-08 at 11:17 +0000, Nicolas Saenz Julienne wrote:
> VSM is also a user of memory attributes, so let it use
> kvm_set_mem_attributes().
> 
> Signed-off-by: Nicolas Saenz Julienne <nsaenz@amazon.com>
> ---
>  arch/x86/kvm/mmu/mmu.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index feca077c0210..a1fbb905258b 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -7265,7 +7265,8 @@ bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
>  	 * Zapping SPTEs in this case ensures KVM will reassess whether or not
>  	 * a hugepage can be used for affected ranges.
>  	 */
> -	if (WARN_ON_ONCE(!kvm_arch_has_private_mem(kvm)))
> +	if (WARN_ON_ONCE(!kvm_arch_has_private_mem(kvm) &&
> +			 !kvm_hv_vsm_enabled(kvm)))
>  		return false;

IMHO on the long term, memory attributes should either be always enabled,
or the above check should became more generic.

But otherwise this patch looks reasonable.

>  
>  	return kvm_unmap_gfn_range(kvm, range);
> @@ -7322,7 +7323,8 @@ bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
>  	 * a range that has PRIVATE GFNs, and conversely converting a range to
>  	 * SHARED may now allow hugepages.
>  	 */
> -	if (WARN_ON_ONCE(!kvm_arch_has_private_mem(kvm)))
> +	if (WARN_ON_ONCE(!kvm_arch_has_private_mem(kvm) &&
> +			 !kvm_hv_vsm_enabled(kvm)))
>  		return false;
>  
>  	/*

Best regards,
	Maxim Levitsky