Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:1 as permitted sender) client-ip=2620:137:e000::3:1;
Message-ID: <31cd6a37f565e07f3890027b3b3305a225f84956.camel@redhat.com>
Subject: Re: [RFC 17/33] KVM: x86/mmu: Allow setting memory attributes if
 VSM enabled
From:   Maxim Levitsky <mlevitsk@redhat.com>
To:     Nicolas Saenz Julienne <nsaenz@amazon.com>, kvm@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org,
        pbonzini@redhat.com, seanjc@google.com, vkuznets@redhat.com,
        anelkz@amazon.com, graf@amazon.com, dwmw@amazon.co.uk,
        jgowans@amazon.com, corbert@lwn.net, kys@microsoft.com,
        haiyangz@microsoft.com, decui@microsoft.com, x86@kernel.org,
        linux-doc@vger.kernel.org
Date:   Tue, 28 Nov 2023 09:39:49 +0200
In-Reply-To: <20231108111806.92604-18-nsaenz@amazon.com>
References: <20231108111806.92604-1-nsaenz@amazon.com>
         <20231108111806.92604-18-nsaenz@amazon.com>
Content-Type: text/plain; charset="UTF-8"
User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) 
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Precedence: bulk

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