linux-kernel - [PATCH v8 01/10] KVM: SEV: Disable SEV-SNP support on initialization failure

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Message-ID: <20250305230000.231025-2-prsampat@amd.com>
Date: Wed, 5 Mar 2025 16:59:51 -0600
From: "Pratik R. Sampat" <prsampat@....com>
To: <linux-kernel@...r.kernel.org>, <x86@...nel.org>, <kvm@...r.kernel.org>,
	<linux-kselftest@...r.kernel.org>
CC: <seanjc@...gle.com>, <pbonzini@...hat.com>, <thomas.lendacky@....com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>, <shuah@...nel.org>, <pgonda@...gle.com>,
	<ashish.kalra@....com>, <nikunj@....com>, <pankaj.gupta@....com>,
	<michael.roth@....com>, <sraithal@....com>, <prsampat@....com>
Subject: [PATCH v8 01/10] KVM: SEV: Disable SEV-SNP support on initialization failure

During platform init, SNP initialization may fail for several reasons,
such as firmware command failures and incompatible versions. However,
the KVM capability may continue to advertise support for it. During
setup, query the SNP platform status to obtain the initialization state
and use it as an additional condition to determine support for SEV-SNP.

Fixes: 1dfe571c12cf ("KVM: SEV: Add initial SEV-SNP support")
Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Pratik R. Sampat <prsampat@....com>
---
v7..v8:
* Avoid exporting yet another API from CCP. Instead query
  SNP_PLATFORM_STATUS to get the current the initialization state
  within KVM (Tom)
---
 arch/x86/kvm/svm/sev.c | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 0dbb25442ec1..e21c3aa6f592 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2950,6 +2950,32 @@ void __init sev_set_cpu_caps(void)
 	}
 }
 
+static bool snp_initialized(void)
+{
+	struct sev_user_data_snp_status *status;
+	struct sev_data_snp_addr buf;
+	bool initialized = false;
+	void *data;
+	int error;
+
+	data = snp_alloc_firmware_page(GFP_KERNEL_ACCOUNT);
+	if (!data)
+		return initialized;
+
+	buf.address = __psp_pa(data);
+	if (sev_do_cmd(SEV_CMD_SNP_PLATFORM_STATUS, &buf, &error))
+		goto out;
+
+	status = (struct sev_user_data_snp_status *)data;
+	if (status->state)
+		initialized = true;
+
+out:
+	snp_free_firmware_page(data);
+
+	return initialized;
+}
+
 void __init sev_hardware_setup(void)
 {
 	unsigned int eax, ebx, ecx, edx, sev_asid_count, sev_es_asid_count;
@@ -3050,7 +3076,9 @@ void __init sev_hardware_setup(void)
 	sev_es_asid_count = min_sev_asid - 1;
 	WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV_ES, sev_es_asid_count));
 	sev_es_supported = true;
-	sev_snp_supported = sev_snp_enabled && cc_platform_has(CC_ATTR_HOST_SEV_SNP);
+	sev_snp_supported = (sev_snp_enabled &&
+			    cc_platform_has(CC_ATTR_HOST_SEV_SNP) &&
+			    snp_initialized());
 
 out:
 	if (boot_cpu_has(X86_FEATURE_SEV))
-- 
2.43.0