linux-kernel - [PATCH] x86/sev: Make SEV_STATUS available via SYSFS

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Message-ID: <20250305105234.235553-1-joro@8bytes.org>
Date: Wed,  5 Mar 2025 11:52:34 +0100
From: Joerg Roedel <joro@...tes.org>
To: x86@...nel.org
Cc: hpa@...or.com,
	Tom Lendacky <thomas.lendacky@....com>,
	Nikunj A Dadhania <nikunj@....com>,
	linux-kernel@...r.kernel.org,
	Larry.Dewey@....com,
	Joerg Roedel <jroedel@...e.de>
Subject: [PATCH] x86/sev: Make SEV_STATUS available via SYSFS

From: Joerg Roedel <jroedel@...e.de>

Current user-space tooling which needs access to the SEV_STATUS MSR is
using the MSR module. The use of this module poses a security risk in
any trusted execution environment and is generally discouraged.

Instead, provide an file in SYSFS in the already existing
/sys/devices/system/cpu/sev/ directory to provide the value of the
SEV_STATUS MSR to user-space.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 arch/x86/coco/sev/core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 82492efc5d94..7b23fb803610 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -2678,10 +2678,19 @@ static ssize_t vmpl_show(struct kobject *kobj,
 	return sysfs_emit(buf, "%d\n", snp_vmpl);
 }
 
+static ssize_t sev_status_show(struct kobject *kobj,
+			       struct kobj_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%llx\n", sev_status);
+}
+
 static struct kobj_attribute vmpl_attr = __ATTR_RO(vmpl);
+static struct kobj_attribute sev_status_attr = __ATTR_RO(sev_status);
+
 
 static struct attribute *vmpl_attrs[] = {
 	&vmpl_attr.attr,
+	&sev_status_attr.attr,
 	NULL
 };
 
-- 
2.48.1