From: Zeng Guang <[email protected]> Virtualize Linear Address Space Separation (LASS) by letting the guest enable CR4.LASS[bit 27]. Allow the guest to set CR4.LASS only if LASS is enumerated in the guest's CPUID. Set CR4.LASS in the emulated IA32_VMX_CR4_FIXED1 MSR so that LASS can be enabled in nested VMX operation as well.
Keep CR4.LASS KVM-owned instead of making it guest-owned. LASS is expected to be enabled once per vCPU at boot and rarely toggled at runtime. LASS is enumerated by CPUID.(EAX=07H,ECX=1):EAX.LASS[bit 6] and only works in IA-32e mode. Advertise LASS to userspace on 64-bit kernels and only when it is supported by the host. Notably, it will not be exposed to userspace if the deprecated vsyscall=emulate mode is set on the kernel command line. Signed-off-by: Zeng Guang <[email protected]> Signed-off-by: Binbin Wu <[email protected]> Signed-off-by: Sohil Mehta <[email protected]> --- v4: - Split patch diffs and reworded the commit message - Use X86_64_F() instead of F() --- arch/x86/kvm/cpuid.c | 1 + arch/x86/kvm/regs.h | 4 +++- arch/x86/kvm/vmx/vmx.c | 1 + 3 files changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 9e9cf6538a96..c4dbd00f5e4e 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -1029,6 +1029,7 @@ void kvm_initialize_cpu_caps(void) F(SM4), F(AVX_VNNI), F(AVX512_BF16), + X86_64_F(LASS), F(CMPCCXADD), F(FZRM), F(FSRS), diff --git a/arch/x86/kvm/regs.h b/arch/x86/kvm/regs.h index 447f0ec3e63e..be8621695c41 100644 --- a/arch/x86/kvm/regs.h +++ b/arch/x86/kvm/regs.h @@ -28,7 +28,7 @@ static_assert(!(KVM_POSSIBLE_CR0_GUEST_BITS & X86_CR0_PDPTR_BITS)); | X86_CR4_OSXSAVE | X86_CR4_SMEP | X86_CR4_FSGSBASE \ | X86_CR4_OSXMMEXCPT | X86_CR4_LA57 | X86_CR4_VMXE \ | X86_CR4_SMAP | X86_CR4_PKE | X86_CR4_UMIP \ - | X86_CR4_LAM_SUP | X86_CR4_CET)) + | X86_CR4_LAM_SUP | X86_CR4_CET | X86_CR4_LASS)) #define CR8_RESERVED_BITS (~(unsigned long)X86_CR8_TPR) @@ -405,6 +405,8 @@ static inline bool __kvm_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) __reserved_bits |= X86_CR4_PCIDE; \ if (!__cpu_has(__c, X86_FEATURE_LAM)) \ __reserved_bits |= X86_CR4_LAM_SUP; \ + if (!__cpu_has(__c, X86_FEATURE_LASS)) \ + __reserved_bits |= X86_CR4_LASS; \ if (!__cpu_has(__c, X86_FEATURE_SHSTK) && \ !__cpu_has(__c, X86_FEATURE_IBT)) \ __reserved_bits |= X86_CR4_CET; \ diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index ecd105f35c78..3082195906da 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -7885,6 +7885,7 @@ static void nested_vmx_cr_fixed1_bits_update(struct kvm_vcpu *vcpu) entry = kvm_find_cpuid_entry_index(vcpu, 0x7, 1); cr4_fixed1_update(X86_CR4_LAM_SUP, eax, feature_bit(LAM)); + cr4_fixed1_update(X86_CR4_LASS, eax, feature_bit(LASS)); #undef cr4_fixed1_update } -- 2.43.0
