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@xxxxxxx>
Signed-off-by: Eric Van Tassell <Eric.VanTassell@xxxxxxx>
Signed-off-by: Pavan Kumar Paluri <papaluri@xxxxxxx>
Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
Documentation/arch/x86/x86_64/boot-options.rst | 5 +++++
arch/x86/virt/svm/cmdline.c | 7 +++++++
2 files changed, 12 insertions(+)
diff --git a/Documentation/arch/x86/x86_64/boot-options.rst b/Documentation/arch/x86/x86_64/boot-options.rst
index 98d4805f0823..d69e3cfbdba5 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 add4bae3ebef..13e04547f4df 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 +26,12 @@ 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
