Provide "nosnp" boot option via "sev=nosnp" kernel command line to prevent SEV-SNP [1] capable host kernel from enabling SEV-SNP and initializing Reverse Map Table (RMP) Setting 'nosnp' avoids the RMP check overhead in memory accesses when users do not want to run SEV-SNP guests. On providing sev=nosnp via kernel command line: cat /sys/module/kvm_amd/parameters/sev_snp should be "N". The patchset is based on tip/master. Reference: [1] https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/programmer-references/24593.pdf Changelog: ========= v5: * Update cover-letter and Documentation to include information on why nosnp command line option is required (Dave Hansen) * Remove <asm/cache.h> stray header introduced in the previous versions because of __read_mostly attribute that is now moved into virt/svm/cmdline.c * Link: https://lore.kernel.org/all/20240930231102.123403-1-papaluri@xxxxxxx/ v4: * Move __read_mostly attribute to place where sev_cfg is declared (Tom) * Link: https://lore.kernel.org/all/20240922033626.29038-1-papaluri@xxxxxxx/ Pavan Kumar Paluri (2): x86, KVM:SVM: Move sev specific parsing into arch/x86/virt/svm x86 KVM:SVM: Provide "nosnp" boot option for sev kernel command line .../arch/x86/x86_64/boot-options.rst | 5 +++ arch/x86/coco/sev/core.c | 44 ------------------- arch/x86/include/asm/sev-common.h | 27 ++++++++++++ arch/x86/virt/svm/Makefile | 1 + arch/x86/virt/svm/cmdline.c | 39 ++++++++++++++++ 5 files changed, 72 insertions(+), 44 deletions(-) create mode 100644 arch/x86/virt/svm/cmdline.c base-commit: 00d91979d23c88d3f50870e22fc9cec3f5e26a2a -- 2.34.1
