Re: [PATCH 13/18] KVM: x86/mmu: Avoid warning when installing non-private memory attributes

[Sean Christopherson <seanjc@google.com>]

On Sun, Jun 09, 2024, Nicolas Saenz Julienne wrote:
> In preparation to introducing RWX memory attributes, make sure
> user-space is attempting to install a memory attribute with
> KVM_MEMORY_ATTRIBUTE_PRIVATE before throwing a warning on systems with
> no private memory support.
> 
> Signed-off-by: Nicolas Saenz Julienne <nsaenz@amazon.com>
> ---
>  arch/x86/kvm/mmu/mmu.c | 8 ++++++--
>  virt/kvm/kvm_main.c    | 1 +
>  2 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index b0c210b96419f..d56c04fbdc66b 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -7359,6 +7359,9 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
>  bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
>  					struct kvm_gfn_range *range)
>  {
> +	unsigned long attrs = range->arg.attributes;
> +	bool priv_attr = attrs & KVM_MEMORY_ATTRIBUTE_PRIVATE;

It's probably worth making this check generic straightaway, e.g. build and then
check the set of allowed attributes, similar to how check_memory_region_flags()
builds and checks the set of allowed flags.