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Message-ID: <5048d1bab32530214e7f3e4d73a4756cf374dee6.1751397223.git.ashish.kalra@amd.com>
Date: Tue, 1 Jul 2025 20:15:21 +0000
From: Ashish Kalra <Ashish.Kalra@....com>
To: <corbet@....net>, <seanjc@...gle.com>, <pbonzini@...hat.com>,
<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
<dave.hansen@...ux.intel.com>, <x86@...nel.org>, <hpa@...or.com>,
<thomas.lendacky@....com>, <john.allen@....com>,
<herbert@...dor.apana.org.au>, <davem@...emloft.net>,
<akpm@...ux-foundation.org>, <rostedt@...dmis.org>, <paulmck@...nel.org>
CC: <nikunj@....com>, <Neeraj.Upadhyay@....com>, <aik@....com>,
<ardb@...nel.org>, <michael.roth@....com>, <arnd@...db.de>,
<linux-doc@...r.kernel.org>, <linux-crypto@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>
Subject: [PATCH v5 3/7] crypto: ccp - Add support for SNP_FEATURE_INFO command
From: Ashish Kalra <ashish.kalra@....com>
The FEATURE_INFO command provides hypervisors a programmatic means to
learn about the supported features of the currently loaded firmware.
FEATURE_INFO command leverages the same mechanism as the CPUID
instruction. Instead of using the CPUID instruction to retrieve
Fn8000_0024, software can use FEATURE_INFO.
Switch to using SNP platform status instead of SEV platform status if
SNP is enabled and cache SNP platform status and feature information
from CPUID 0x7fff_0024, sub-function 0, in the sev_device structure.
Suggested-by: Tom Lendacky <thomas.lendacky@....com>
Signed-off-by: Ashish Kalra <ashish.kalra@....com>
---
drivers/crypto/ccp/sev-dev.c | 72 ++++++++++++++++++++++++++++++++++++
drivers/crypto/ccp/sev-dev.h | 3 ++
include/linux/psp-sev.h | 29 +++++++++++++++
3 files changed, 104 insertions(+)
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 5a2e1651d171..d1517a91a27d 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -233,6 +233,7 @@ static int sev_cmd_buffer_len(int cmd)
case SEV_CMD_SNP_GUEST_REQUEST: return sizeof(struct sev_data_snp_guest_request);
case SEV_CMD_SNP_CONFIG: return sizeof(struct sev_user_data_snp_config);
case SEV_CMD_SNP_COMMIT: return sizeof(struct sev_data_snp_commit);
+ case SEV_CMD_SNP_FEATURE_INFO: return sizeof(struct sev_data_snp_feature_info);
default: return 0;
}
@@ -1073,6 +1074,67 @@ static void snp_set_hsave_pa(void *arg)
wrmsrq(MSR_VM_HSAVE_PA, 0);
}
+static int snp_get_platform_data(struct sev_device *sev, int *error)
+{
+ struct sev_data_snp_feature_info snp_feat_info;
+ struct snp_feature_info *feat_info;
+ struct sev_data_snp_addr buf;
+ struct page *page;
+ int rc;
+
+ /*
+ * This function is expected to be called before SNP is not
+ * initialized.
+ */
+ if (sev->snp_initialized)
+ return -EINVAL;
+
+ buf.address = __psp_pa(&sev->snp_plat_status);
+ rc = sev_do_cmd(SEV_CMD_SNP_PLATFORM_STATUS, &buf, error);
+ if (rc) {
+ dev_err(sev->dev, "SNP PLATFORM_STATUS command failed, ret = %d, error = %#x\n",
+ rc, *error);
+ return rc;
+ }
+
+ sev->api_major = sev->snp_plat_status.api_major;
+ sev->api_minor = sev->snp_plat_status.api_minor;
+ sev->build = sev->snp_plat_status.build_id;
+
+ /*
+ * Do feature discovery of the currently loaded firmware,
+ * and cache feature information from CPUID 0x8000_0024,
+ * sub-function 0.
+ */
+ if (!sev->snp_plat_status.feature_info)
+ return 0;
+
+ /*
+ * Use dynamically allocated structure for the SNP_FEATURE_INFO
+ * command to ensure structure is 8-byte aligned, and does not
+ * cross a page boundary.
+ */
+ page = alloc_page(GFP_KERNEL);
+ if (!page)
+ return -ENOMEM;
+
+ feat_info = page_address(page);
+ snp_feat_info.length = sizeof(snp_feat_info);
+ snp_feat_info.ecx_in = 0;
+ snp_feat_info.feature_info_paddr = __psp_pa(feat_info);
+
+ rc = sev_do_cmd(SEV_CMD_SNP_FEATURE_INFO, &snp_feat_info, error);
+ if (!rc)
+ sev->snp_feat_info_0 = *feat_info;
+ else
+ dev_err(sev->dev, "SNP FEATURE_INFO command failed, ret = %d, error = %#x\n",
+ rc, *error);
+
+ __free_page(page);
+
+ return rc;
+}
+
static int snp_filter_reserved_mem_regions(struct resource *rs, void *arg)
{
struct sev_data_range_list *range_list = arg;
@@ -1599,6 +1661,16 @@ static int sev_get_api_version(void)
struct sev_user_data_status status;
int error = 0, ret;
+ /*
+ * Cache SNP platform status and SNP feature information
+ * if SNP is available.
+ */
+ if (cc_platform_has(CC_ATTR_HOST_SEV_SNP)) {
+ ret = snp_get_platform_data(sev, &error);
+ if (ret)
+ return 1;
+ }
+
ret = sev_platform_status(&status, &error);
if (ret) {
dev_err(sev->dev,
diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
index 24dd8ff8afaa..5aed2595c9ae 100644
--- a/drivers/crypto/ccp/sev-dev.h
+++ b/drivers/crypto/ccp/sev-dev.h
@@ -58,6 +58,9 @@ struct sev_device {
bool snp_initialized;
struct sev_user_data_status sev_plat_status;
+
+ struct sev_user_data_snp_status snp_plat_status;
+ struct snp_feature_info snp_feat_info_0;
};
int sev_dev_init(struct psp_device *psp);
diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
index 0f5f94137f6d..935547c26985 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -107,6 +107,7 @@ enum sev_cmd {
SEV_CMD_SNP_DOWNLOAD_FIRMWARE_EX = 0x0CA,
SEV_CMD_SNP_COMMIT = 0x0CB,
SEV_CMD_SNP_VLEK_LOAD = 0x0CD,
+ SEV_CMD_SNP_FEATURE_INFO = 0x0CE,
SEV_CMD_MAX,
};
@@ -814,6 +815,34 @@ struct sev_data_snp_commit {
u32 len;
} __packed;
+/**
+ * struct sev_data_snp_feature_info - SEV_SNP_FEATURE_INFO structure
+ *
+ * @length: len of the command buffer read by the PSP
+ * @ecx_in: subfunction index
+ * @feature_info_paddr : SPA of the FEATURE_INFO structure
+ */
+struct sev_data_snp_feature_info {
+ u32 length;
+ u32 ecx_in;
+ u64 feature_info_paddr;
+} __packed;
+
+/**
+ * struct feature_info - FEATURE_INFO structure
+ *
+ * @eax: output of SNP_FEATURE_INFO command
+ * @ebx: output of SNP_FEATURE_INFO command
+ * @ecx: output of SNP_FEATURE_INFO command
+ * #edx: output of SNP_FEATURE_INFO command
+ */
+struct snp_feature_info {
+ u32 eax;
+ u32 ebx;
+ u32 ecx;
+ u32 edx;
+} __packed;
+
#ifdef CONFIG_CRYPTO_DEV_SP_PSP
/**
--
2.34.1
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