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| author | Pavan Kumar Paluri <papaluri@amd.com> | 2024-10-14 08:09:48 -0500 |
|---|---|---|
| committer | Borislav Petkov (AMD) <bp@alien8.de> | 2024-10-15 20:22:18 +0200 |
| commit | 2db67aaca578ec4998b78dc85e2af214bc2e2770 (patch) | |
| tree | 0af717dc76ae856cf026e11363533ff3be4bde9e | |
| parent | 4ae47fa7e8f95be17d4ff9c317a1193bbb4a3998 (diff) | |
| download | lwn-2db67aaca578ec4998b78dc85e2af214bc2e2770.tar.gz lwn-2db67aaca578ec4998b78dc85e2af214bc2e2770.zip | |
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@amd.com>
Signed-off-by: Eric Van Tassell <Eric.VanTassell@amd.com>
Signed-off-by: Pavan Kumar Paluri <papaluri@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20241014130948.1476946-3-papaluri@amd.com
| -rw-r--r-- | Documentation/arch/x86/x86_64/boot-options.rst | 5 | ||||
| -rw-r--r-- | arch/x86/virt/svm/cmdline.c | 12 |
2 files changed, 17 insertions, 0 deletions
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..affa2759fa20 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); } |