linux-kernel - Re: [PATCH v16 05/13] x86/sev: Add Secure TSC support for SNP guests

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <c7165d80-ab7f-425b-8323-3f759e1e41a6@amd.com>
Date: Wed, 8 Jan 2025 13:17:11 +0530
From: "Nikunj A. Dadhania" <nikunj@....com>
To: Borislav Petkov <bp@...en8.de>, Tom Lendacky <thomas.lendacky@....com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org,
 mingo@...hat.com, tglx@...utronix.de, dave.hansen@...ux.intel.com,
 pgonda@...gle.com, seanjc@...gle.com, pbonzini@...hat.com,
 francescolavra.fl@...il.com
Subject: Re: [PATCH v16 05/13] x86/sev: Add Secure TSC support for SNP guests



On 1/8/2025 12:48 AM, Borislav Petkov wrote:
> On Tue, Jan 07, 2025 at 12:53:26PM -0600, Tom Lendacky wrote:
>> Yes, but from a readability point of view this makes it perfectly clear
>> that Secure TSC is only for SNP guests.
> 
> That would mean that we need to check SNP with every SNP-specific feature
> which would be just silly. And all SNP feature bits have "SNP" in the same
> so...
> 

Right, here is the updated diff:

diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
index 715c2c09582f..d6647953590b 100644
--- a/arch/x86/coco/core.c
+++ b/arch/x86/coco/core.c
@@ -98,8 +98,7 @@ static bool noinstr amd_cc_platform_has(enum cc_attr attr)
 		return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
 
 	case CC_ATTR_GUEST_SNP_SECURE_TSC:
-		return (sev_status & MSR_AMD64_SEV_SNP_ENABLED) &&
-			(sev_status & MSR_AMD64_SNP_SECURE_TSC);
+		return sev_status & MSR_AMD64_SNP_SECURE_TSC;
 
 	case CC_ATTR_HOST_SEV_SNP:
 		return cc_flags.host_sev_snp;
diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 00a0ac3baab7..763cfeb65b2f 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -3218,7 +3218,8 @@ static int __init snp_get_tsc_info(void)
 
 void __init snp_secure_tsc_prepare(void)
 {
-	if (!cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC))
+	if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP) ||
+	    !cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC))
 		return;
 
 	if (snp_get_tsc_info()) {