[PATCH v6 2/2] x86 KVM:SVM: Provide "nosnp" boot option for sev kernel command line
From: Pavan Kumar Paluri <hidden>
Date: 2024-10-10 12:15:29
Also in:
linux-doc, lkml
Subsystem:
documentation, the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Jonathan Corbet, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
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 <redacted> Signed-off-by: Eric Van Tassell <redacted> Signed-off-by: Pavan Kumar Paluri <redacted> Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com> --- 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 9640507342e0..313415d6f53f 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 __read_mostly;
@@ -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