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Message-ID: <20240905143056.48216-3-papaluri@amd.com>
Date: Thu, 5 Sep 2024 09:30:56 -0500
From: Pavan Kumar Paluri <papaluri@....com>
To: <linux-kernel@...r.kernel.org>
CC: <linux-doc@...r.kernel.org>, Borislav Petkov <bp@...en8.de>, "Thomas
Gleixner" <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Dave Hansen
<dave.hansen@...ux.intel.com>, Eric Van Tassell <Eric.VanTassell@....com>,
Tom Lendacky <thomas.lendacky@....com>, Ashish Kalra <ashish.kalra@....com>,
Michael Roth <michael.roth@....com>, "H . Peter Anvin" <hpa@...or.com>,
"Peter Zijlstra" <peterz@...radead.org>, Pavan Kumar Paluri
<papaluri@....com>
Subject: [PATCH v3 2/2] x86 KVM:SVM: Provide "nosnp" boot option for sev kernel command line
Provide a "nosnp" kernel command line option to prevent enabling of the
RMP and SEV-SNP features in the host/hypervisor. Not initializing the
RMP removes system overhead associated with RMP checks.
Co-developed-by: Eric Van Tassell <Eric.VanTassell@....com>
Signed-off-by: Eric Van Tassell <Eric.VanTassell@....com>
Signed-off-by: Pavan Kumar Paluri <papaluri@....com>
Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
---
Documentation/arch/x86/x86_64/boot-options.rst | 3 +++
arch/x86/virt/svm/cmdline.c | 7 +++++++
2 files changed, 10 insertions(+)
diff --git a/Documentation/arch/x86/x86_64/boot-options.rst b/Documentation/arch/x86/x86_64/boot-options.rst
index 137432d34109..3d4e9a7dccf2 100644
--- a/Documentation/arch/x86/x86_64/boot-options.rst
+++ b/Documentation/arch/x86/x86_64/boot-options.rst
@@ -317,3 +317,6 @@ The available options are:
debug
Enable debug messages.
+
+ nosnp
+ Do not enable SEV-SNP (applies to host/hypervisor only).
diff --git a/arch/x86/virt/svm/cmdline.c b/arch/x86/virt/svm/cmdline.c
index 964677ab02d6..454574539c49 100644
--- a/arch/x86/virt/svm/cmdline.c
+++ b/arch/x86/virt/svm/cmdline.c
@@ -11,6 +11,7 @@
#include <linux/printk.h>
#include <asm/sev-common.h>
+#include <asm/cpufeature.h>
struct sev_config sev_cfg;
@@ -24,6 +25,12 @@ static int __init init_sev_config(char *str)
continue;
}
+ if (!strcmp(s, "nosnp")) {
+ setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);
+ cc_platform_clear(CC_ATTR_HOST_SEV_SNP);
+ continue;
+ }
+
pr_info("SEV command-line option '%s' was not recognized\n", s);
}
--
2.34.1
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