From: "Tycho Andersen (AMD)" <tycho@kernel.org>

In some configurations, the firmware does not support all VM types. Do an
SNP_VERIFY_MITIGATION to determine if the mitigation for CVE-2025-48514 is
active, and if so, turn off the SEV_ES bit.

Signed-off-by: Tycho Andersen (AMD) <tycho@kernel.org>
---
 drivers/crypto/ccp/sev-dev.c | 83 ++++++++++++++++++++++++++++++++++++
 include/linux/psp-sev.h      |  9 ++++
 2 files changed, 92 insertions(+)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 9eba3fe1a27f..79610617a38d 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -2930,3 +2930,86 @@ void sev_pci_exit(void)
 
 	sev_firmware_shutdown(sev);
 }
+
+static int snp_verify_mitigation(struct sev_device *sev, u64 vector, u64 *verified)
+{
+	struct sev_data_snp_verify_mitigation data = {0};
+	struct snp_verify_mitigation_dst *dst;
+	struct page *p;
+	int rc, error = 0;
+
+	if (!sev->snp_plat_status.feature_info ||
+	    !(sev->snp_feat_info_0.ecx & SNP_VERIFY_MITIGATION_SUPPORTED)) {
+		return -EOPNOTSUPP;
+	}
+
+	p = __snp_alloc_firmware_pages(GFP_KERNEL, 0, true);
+	if (!p)
+		return -ENOMEM;
+	dst = page_address(p);
+
+	data.length = sizeof(data);
+	data.subcommand = SNP_MIT_SUBCMD_REQ_VERIFY;
+	data.vector = vector;
+	data.dst_paddr_en = 1;
+	data.dst_paddr = __psp_pa(dst);
+
+	rc = sev_do_cmd(SEV_CMD_SNP_VERIFY_MITIGATION, &data, &error);
+	if (rc < 0) {
+		if (error)
+			dev_err(sev->dev, "VERIFY_MITIGATION error %d\n", error);
+		goto reclaim_pages;
+	}
+
+	rc = -EIO;
+	if (dst->mit_failure_status) {
+		dev_err(sev->dev, "VERIFY_MITIGATION failure status %d\n", dst->mit_failure_status);
+		goto reclaim_pages;
+	}
+
+	*verified = dst->mit_verified_vector;
+	rc = 0;
+
+reclaim_pages:
+	__snp_free_firmware_pages(p, 0, true);
+	return rc;
+}
+
+int sev_firmware_supported_vm_types(void)
+{
+	int rc, supported_vm_types = 0;
+	struct sev_device *sev;
+	u64 verified = 0;
+
+	if (!psp_master || !psp_master->sev_data)
+		return supported_vm_types;
+	sev = psp_master->sev_data;
+
+	supported_vm_types |= BIT(KVM_X86_SEV_VM);
+	supported_vm_types |= BIT(KVM_X86_SEV_ES_VM);
+
+	if (!sev->snp_initialized)
+		return supported_vm_types;
+
+	supported_vm_types |= BIT(KVM_X86_SNP_VM);
+
+	rc = snp_verify_mitigation(sev, SNP_MIT_VEC_CVE_2025_48514, &verified);
+	if (rc < 0) {
+		/*
+		 * Older firmware that doesn't support VERIFY_MITIGATION won't
+		 * have the mitigation for this CVE, so all types are supported.
+		 */
+		if (rc == -EOPNOTSUPP)
+			return supported_vm_types;
+		dev_err(sev->dev, "Unable to determine supported vm types: %d\n", rc);
+		return supported_vm_types;
+	}
+
+	/* This mitigation disables SEV-ES guests when present */
+	if (verified & SNP_MIT_VEC_CVE_2025_48514)
+		supported_vm_types &= ~BIT(KVM_X86_SEV_ES_VM);
+
+	return supported_vm_types;
+
+}
+EXPORT_SYMBOL_FOR_MODULES(sev_firmware_supported_vm_types, "kvm-amd");
diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
index 2b4b56632b4e..07ce49b31ba2 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -611,6 +611,12 @@ struct sev_data_snp_verify_mitigation {
 #define SNP_MIT_SUBCMD_REQ_STATUS	0x0
 #define SNP_MIT_SUBCMD_REQ_VERIFY	0x1
 
+/*
+ * For CVE-2025-48514 defined in AMD-SB-3023
+ * https://www.amd.com/en/resources/product-security/bulletin/amd-sb-3023.html
+ */
+#define SNP_MIT_VEC_CVE_2025_48514		BIT(3)
+
 /**
  * struct snp_verify_mitigation_dst - mitigation result vectors
  *
@@ -1092,6 +1098,7 @@ void snp_free_firmware_page(void *addr);
 void sev_platform_shutdown(void);
 bool sev_is_snp_ciphertext_hiding_supported(void);
 u64 sev_get_snp_policy_bits(void);
+int sev_firmware_supported_vm_types(void);
 
 #else	/* !CONFIG_CRYPTO_DEV_SP_PSP */
 
@@ -1135,6 +1142,8 @@ static inline void sev_platform_shutdown(void) { }
 
 static inline bool sev_is_snp_ciphertext_hiding_supported(void) { return false; }
 
+static inline int sev_firmware_supported_vm_types(void) { return 0; }
+
 #endif	/* CONFIG_CRYPTO_DEV_SP_PSP */
 
 #endif	/* __PSP_SEV_H__ */
-- 
2.53.0

On Tue, Mar 03, 2026 at 12:15:07PM -0700, Tycho Andersen wrote:
> +/*
> + * For CVE-2025-48514 defined in AMD-SB-3023
> + * https://www.amd.com/en/resources/product-security/bulletin/amd-sb-3023.html
> + */
> +#define SNP_MIT_VEC_CVE_2025_48514		BIT(3)

It turns out that the public security bulletin is wrong, and this is
not the right way to check for this. I will respin the series with a
fix.

Tycho