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Message-ID: <172901760536.1442.16894857501256114810.tip-bot2@tip-bot2>
Date: Tue, 15 Oct 2024 18:40:05 -0000
From: "tip-bot2 for Pavan Kumar Paluri" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Eric Van Tassell <Eric.VanTassell@....com>,
Pavan Kumar Paluri <papaluri@....com>, "Borislav Petkov (AMD)" <bp@...en8.de>,
Tom Lendacky <thomas.lendacky@....com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: x86/sev] x86/virt: Provide "nosnp" boot option for sev kernel
command line
The following commit has been merged into the x86/sev branch of tip:
Commit-ID: 2db67aaca578ec4998b78dc85e2af214bc2e2770
Gitweb: https://git.kernel.org/tip/2db67aaca578ec4998b78dc85e2af214bc2e2770
Author: Pavan Kumar Paluri <papaluri@....com>
AuthorDate: Mon, 14 Oct 2024 08:09:48 -05:00
Committer: Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Tue, 15 Oct 2024 20:22:18 +02:00
x86/virt: 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.
[ bp: Actually make it a HV-only cmdline option. ]
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>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
Link: https://lore.kernel.org/r/20241014130948.1476946-3-papaluri@amd.com
---
Documentation/arch/x86/x86_64/boot-options.rst | 5 +++++
arch/x86/virt/svm/cmdline.c | 12 ++++++++++++
2 files changed, 17 insertions(+)
diff --git a/Documentation/arch/x86/x86_64/boot-options.rst b/Documentation/arch/x86/x86_64/boot-options.rst
index 98d4805..d69e3cf 100644
--- a/Documentation/arch/x86/x86_64/boot-options.rst
+++ b/Documentation/arch/x86/x86_64/boot-options.rst
@@ -305,3 +305,8 @@ The available options are:
debug
Enable debug messages.
+
+ nosnp
+ Do not enable SEV-SNP (applies to host/hypervisor only). Setting
+ 'nosnp' avoids the RMP check overhead in memory accesses when
+ users do not want to run SEV-SNP guests.
diff --git a/arch/x86/virt/svm/cmdline.c b/arch/x86/virt/svm/cmdline.c
index add4bae..affa275 100644
--- a/arch/x86/virt/svm/cmdline.c
+++ b/arch/x86/virt/svm/cmdline.c
@@ -10,6 +10,7 @@
#include <linux/string.h>
#include <linux/printk.h>
#include <linux/cache.h>
+#include <linux/cpufeature.h>
#include <asm/sev-common.h>
@@ -25,6 +26,17 @@ static int __init init_sev_config(char *str)
continue;
}
+ if (!strcmp(s, "nosnp")) {
+ if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR)) {
+ setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);
+ cc_platform_clear(CC_ATTR_HOST_SEV_SNP);
+ continue;
+ } else {
+ goto warn;
+ }
+ }
+
+warn:
pr_info("SEV command-line option '%s' was not recognized\n", s);
}
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