From b1a3c366cbc783d6600b357ccfec2f440eed5453 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 9 Jan 2024 16:23:40 -0800 Subject: x86/cpu: Add a VMX flag to enumerate 5-level EPT support to userspace Add a VMX flag in /proc/cpuinfo, ept_5level, so that userspace can query whether or not the CPU supports 5-level EPT paging. EPT capabilities are enumerated via MSR, i.e. aren't accessible to userspace without help from the kernel, and knowing whether or not 5-level EPT is supported is useful for debug, triage, testing, etc. For example, when EPT is enabled, bits 51:48 of guest physical addresses are consumed by the CPU if and only if 5-level EPT is enabled. For CPUs with MAXPHYADDR > 48, KVM *can't* map all legal guest memory without 5-level EPT, making 5-level EPT support valuable information for userspace. Reported-by: Yi Lai Cc: Tao Su Cc: Xudong Hao Link: https://lore.kernel.org/r/20240110002340.485595-1-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/include/asm/vmxfeatures.h | 1 + arch/x86/kernel/cpu/feat_ctl.c | 2 ++ 2 files changed, 3 insertions(+) (limited to 'arch/x86') diff --git a/arch/x86/include/asm/vmxfeatures.h b/arch/x86/include/asm/vmxfeatures.h index c6a7eed03914..266daf5b5b84 100644 --- a/arch/x86/include/asm/vmxfeatures.h +++ b/arch/x86/include/asm/vmxfeatures.h @@ -25,6 +25,7 @@ #define VMX_FEATURE_EPT_EXECUTE_ONLY ( 0*32+ 17) /* "ept_x_only" EPT entries can be execute only */ #define VMX_FEATURE_EPT_AD ( 0*32+ 18) /* EPT Accessed/Dirty bits */ #define VMX_FEATURE_EPT_1GB ( 0*32+ 19) /* 1GB EPT pages */ +#define VMX_FEATURE_EPT_5LEVEL ( 0*32+ 20) /* 5-level EPT paging */ /* Aggregated APIC features 24-27 */ #define VMX_FEATURE_FLEXPRIORITY ( 0*32+ 24) /* TPR shadow + virt APIC */ diff --git a/arch/x86/kernel/cpu/feat_ctl.c b/arch/x86/kernel/cpu/feat_ctl.c index 03851240c3e3..1640ae76548f 100644 --- a/arch/x86/kernel/cpu/feat_ctl.c +++ b/arch/x86/kernel/cpu/feat_ctl.c @@ -72,6 +72,8 @@ static void init_vmx_capabilities(struct cpuinfo_x86 *c) c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_AD); if (ept & VMX_EPT_1GB_PAGE_BIT) c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_1GB); + if (ept & VMX_EPT_PAGE_WALK_5_BIT) + c->vmx_capability[MISC_FEATURES] |= VMX_F(EPT_5LEVEL); /* Synthetic APIC features that are aggregates of multiple features. */ if ((c->vmx_capability[PRIMARY_CTLS] & VMX_F(VIRTUAL_TPR)) && -- cgit v1.2.3