Add a flag to track when KVM is actively configuring its CPU caps, and WARN if a cap is set or cleared if KVM isn't in its configuration stage. Modifying CPU caps after {svm,vmx}_set_cpu_caps() can be fatal to KVM, as vendor setup code expects the CPU caps to be frozen at that point, e.g. will do additional configuration based on the caps. Rename kvm_set_cpu_caps() to kvm_initialize_cpu_caps() to pair with the new "finalize", and to make it more obvious that KVM's CPU caps aren't fully configured within the function. Signed-off-by: Sean Christopherson --- arch/x86/kvm/cpuid.c | 10 ++++++++-- arch/x86/kvm/cpuid.h | 12 +++++++++++- arch/x86/kvm/svm/svm.c | 4 +++- arch/x86/kvm/vmx/vmx.c | 4 +++- 4 files changed, 25 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 575244af9c9f..7fe4e58a6ebf 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -36,6 +36,9 @@ u32 kvm_cpu_caps[NR_KVM_CPU_CAPS] __read_mostly; EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_cpu_caps); +bool kvm_is_configuring_cpu_caps __read_mostly; +EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_is_configuring_cpu_caps); + struct cpuid_xstate_sizes { u32 eax; u32 ebx; @@ -826,10 +829,13 @@ do { \ /* DS is defined by ptrace-abi.h on 32-bit builds. */ #undef DS -void kvm_set_cpu_caps(void) +void kvm_initialize_cpu_caps(void) { memset(kvm_cpu_caps, 0, sizeof(kvm_cpu_caps)); + WARN_ON_ONCE(kvm_is_configuring_cpu_caps); + kvm_is_configuring_cpu_caps = true; + BUILD_BUG_ON(sizeof(kvm_cpu_caps) - (NKVMCAPINTS * sizeof(*kvm_cpu_caps)) > sizeof(boot_cpu_data.x86_capability)); @@ -1289,7 +1295,7 @@ void kvm_set_cpu_caps(void) kvm_cpu_cap_clear(X86_FEATURE_RDPID); } } -EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_set_cpu_caps); +EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_initialize_cpu_caps); #undef F #undef SCATTERED_F diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h index d3f5ae15a7ca..039b8e6f40ba 100644 --- a/arch/x86/kvm/cpuid.h +++ b/arch/x86/kvm/cpuid.h @@ -8,7 +8,15 @@ #include extern u32 kvm_cpu_caps[NR_KVM_CPU_CAPS] __read_mostly; -void kvm_set_cpu_caps(void); +extern bool kvm_is_configuring_cpu_caps __read_mostly; + +void kvm_initialize_cpu_caps(void); + +static inline void kvm_finalize_cpu_caps(void) +{ + WARN_ON_ONCE(!kvm_is_configuring_cpu_caps); + kvm_is_configuring_cpu_caps = false; +} void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu); struct kvm_cpuid_entry2 *kvm_find_cpuid_entry2(struct kvm_cpuid_entry2 *entries, @@ -188,6 +196,7 @@ static __always_inline void kvm_cpu_cap_clear(unsigned int x86_feature) { unsigned int x86_leaf = __feature_leaf(x86_feature); + WARN_ON_ONCE(!kvm_is_configuring_cpu_caps); kvm_cpu_caps[x86_leaf] &= ~__feature_bit(x86_feature); } @@ -195,6 +204,7 @@ static __always_inline void kvm_cpu_cap_set(unsigned int x86_feature) { unsigned int x86_leaf = __feature_leaf(x86_feature); + WARN_ON_ONCE(!kvm_is_configuring_cpu_caps); kvm_cpu_caps[x86_leaf] |= __feature_bit(x86_feature); } diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index c00a696dacfc..5f0136dbdde6 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -5305,7 +5305,7 @@ static __init void svm_adjust_mmio_mask(void) static __init void svm_set_cpu_caps(void) { - kvm_set_cpu_caps(); + kvm_initialize_cpu_caps(); kvm_caps.supported_perf_cap = 0; @@ -5389,6 +5389,8 @@ static __init void svm_set_cpu_caps(void) kvm_cpu_cap_clear(X86_FEATURE_MSR_IMM); kvm_setup_xss_caps(); + + kvm_finalize_cpu_caps(); } static __init int svm_hardware_setup(void) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 9f85c3829890..93ec1e6181e4 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -8173,7 +8173,7 @@ static __init u64 vmx_get_perf_capabilities(void) static __init void vmx_set_cpu_caps(void) { - kvm_set_cpu_caps(); + kvm_initialize_cpu_caps(); /* CPUID 0x1 */ if (nested) @@ -8232,6 +8232,8 @@ static __init void vmx_set_cpu_caps(void) } kvm_setup_xss_caps(); + + kvm_finalize_cpu_caps(); } static bool vmx_is_io_intercepted(struct kvm_vcpu *vcpu, -- 2.52.0.457.g6b5491de43-goog