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client-ip=165.204.84.17; helo=SATLEXMB03.amd.com; pr=C Received: from SATLEXMB03.amd.com (165.204.84.17) by CY4PEPF0000EE3A.mail.protection.outlook.com (10.167.242.12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.9073.11 via Frontend Transport; Tue, 26 Aug 2025 15:07:19 +0000 Received: from SATLEXMB05.amd.com (10.181.40.146) by SATLEXMB03.amd.com (10.181.40.144) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Tue, 26 Aug 2025 10:07:19 -0500 Received: from SATLEXMB03.amd.com (10.181.40.144) by SATLEXMB05.amd.com (10.181.40.146) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Tue, 26 Aug 2025 10:07:18 -0500 Received: from [10.252.207.152] (10.180.168.240) by SATLEXMB03.amd.com (10.181.40.144) with Microsoft SMTP Server id 15.1.2507.39 via Frontend Transport; Tue, 26 Aug 2025 10:07:15 -0500 Message-ID: Date: Tue, 26 Aug 2025 20:37:14 +0530 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 2/4] KVM: SEV: Skip SNP-safe allocation when HvInUseWrAllowed is supported To: "Huang, Kai" , "pbonzini@redhat.com" , "seanjc@google.com" CC: "thomas.lendacky@amd.com" , "kvm@vger.kernel.org" , "joao.m.martins@oracle.com" , "santosh.shukla@amd.com" , "bp@alien8.de" References: <20250825152009.3512-1-nikunj@amd.com> <20250825152009.3512-3-nikunj@amd.com> <668a279d908bfdac33a0e64838d4276ec43fcce0.camel@intel.com> Content-Language: en-US From: "Nikunj A. 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Check for this capability to avoid the >> allocation overhead when it's not needed. > > Could you add some text to explain why this is related to PML? PML works fine without this and the change is not linked to PML. This can go as a separate fix. While working on PML which was using the snp_safe_alloc_page(), Tom had suggested to apply the alignment workaround only on the CPUs without HvInUseWrAllowed. > >> >> Suggested-by: Tom Lendacky >> Signed-off-by: Nikunj A Dadhania >> --- >> arch/x86/kvm/svm/sev.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c >> index 2fbdebf79fbb..c5477efc90b9 100644 >> --- a/arch/x86/kvm/svm/sev.c >> +++ b/arch/x86/kvm/svm/sev.c >> @@ -4666,7 +4666,8 @@ struct page *snp_safe_alloc_page_node(int node, gfp_t gfp) >> unsigned long pfn; >> struct page *p; >> >> - if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP)) >> + if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP) || >> + cpu_feature_enabled(X86_FEATURE_HV_INUSE_WR_ALLOWED)) >> return alloc_pages_node(node, gfp | __GFP_ZERO, 0); >> >> /* Regards, Nikunj