diff options
| author | Sean Christopherson <seanjc@google.com> | 2025-09-19 15:32:33 -0700 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2025-09-23 09:19:29 -0700 |
| commit | 1f6f68fcfe43cf26fc0a98fe14e0454cc5c75416 (patch) | |
| tree | cf995fa756c7eb21d3b607f757a4f5dfe9c81d1e | |
| parent | 69cc3e886582891f9c4d5830f18a2664a7f7cf7c (diff) | |
KVM: x86: Disable support for Shadow Stacks if TDP is disabled
Make TDP a hard requirement for Shadow Stacks, as there are no plans to
add Shadow Stack support to the Shadow MMU. E.g. KVM hasn't been taught
to understand the magic Writable=0,Dirty=1 combination that is required
for Shadow Stack accesses, and so enabling Shadow Stacks when using
shadow paging will put the guest into an infinite #PF loop (KVM thinks the
shadow page tables have a valid mapping, hardware says otherwise).
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/r/20250919223258.1604852-27-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
| -rw-r--r-- | arch/x86/kvm/cpuid.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 32fde9e80c28..499c86bd457e 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -955,6 +955,14 @@ void kvm_set_cpu_caps(void) if (!tdp_enabled || !boot_cpu_has(X86_FEATURE_OSPKE)) kvm_cpu_cap_clear(X86_FEATURE_PKU); + /* + * Shadow Stacks aren't implemented in the Shadow MMU. Shadow Stack + * accesses require "magic" Writable=0,Dirty=1 protection, which KVM + * doesn't know how to emulate or map. + */ + if (!tdp_enabled) + kvm_cpu_cap_clear(X86_FEATURE_SHSTK); + kvm_cpu_cap_init(CPUID_7_EDX, F(AVX512_4VNNIW), F(AVX512_4FMAPS), |