From: Sean Christopherson <seanjc@xxxxxxxxxx> Return -ENOMEM back to userspace if allocating the Hyper-V vCPU struct fails when enabling Hyper-V in guest CPUID. Silently ignoring failure means that KVM will not have an up-to-date CPUID cache if allocating the struct succeeds later on, e.g. when activating SynIC. Rejecting the CPUID operation also guarantess that vcpu->arch.hyperv is non-NULL if hyperv_enabled is true, which will allow for additional cleanup, e.g. in the eVMCS code. Note, the initialization needs to be done before CPUID is set, and more subtly before kvm_check_cpuid(), which potentially enables dynamic XFEATURES. Sadly, there's no easy way to avoid exposing Hyper-V details to CPUID or vice versa. Expose kvm_hv_vcpu_init() and the Hyper-V CPUID signature to CPUID instead of exposing cpuid_entry2_find() outside of CPUID code. It's hard to envision kvm_hv_vcpu_init() being misused, whereas cpuid_entry2_find() absolutely shouldn't be used outside of core CPUID code. Fixes: 10d7bf1e46dc ("KVM: x86: hyper-v: Cache guest CPUID leaves determining features availability") Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> --- arch/x86/kvm/cpuid.c | 18 +++++++++++++++++- arch/x86/kvm/hyperv.c | 30 ++++++++++++++---------------- arch/x86/kvm/hyperv.h | 6 +++++- 3 files changed, 36 insertions(+), 18 deletions(-) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 75dcf7a72605..ffdc28684cb7 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -311,6 +311,15 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu) } EXPORT_SYMBOL_GPL(kvm_update_cpuid_runtime); +static bool kvm_cpuid_has_hyperv(struct kvm_cpuid_entry2 *entries, int nent) +{ + struct kvm_cpuid_entry2 *entry; + + entry = cpuid_entry2_find(entries, nent, HYPERV_CPUID_INTERFACE, + KVM_CPUID_INDEX_NOT_SIGNIFICANT); + return entry && entry->eax == HYPERV_CPUID_SIGNATURE_EAX; +} + static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) { struct kvm_lapic *apic = vcpu->arch.apic; @@ -341,7 +350,8 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) vcpu->arch.cr4_guest_rsvd_bits = __cr4_reserved_bits(guest_cpuid_has, vcpu); - kvm_hv_set_cpuid(vcpu); + kvm_hv_set_cpuid(vcpu, kvm_cpuid_has_hyperv(vcpu->arch.cpuid_entries, + vcpu->arch.cpuid_nent)); /* Invoke the vendor callback only after the above state is updated. */ static_call(kvm_x86_vcpu_after_set_cpuid)(vcpu); @@ -404,6 +414,12 @@ static int kvm_set_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *e2, return 0; } + if (kvm_cpuid_has_hyperv(e2, nent)) { + r = kvm_hv_vcpu_init(vcpu); + if (r) + return r; + } + r = kvm_check_cpuid(vcpu, e2, nent); if (r) return r; diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 8aadd31ed058..bf4729e8cc80 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -38,9 +38,6 @@ #include "irq.h" #include "fpu.h" -/* "Hv#1" signature */ -#define HYPERV_CPUID_SIGNATURE_EAX 0x31237648 - #define KVM_HV_MAX_SPARSE_VCPU_SET_BITS DIV_ROUND_UP(KVM_MAX_VCPUS, 64) static void stimer_mark_pending(struct kvm_vcpu_hv_stimer *stimer, @@ -934,7 +931,7 @@ static void stimer_init(struct kvm_vcpu_hv_stimer *stimer, int timer_index) stimer_prepare_msg(stimer); } -static int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu) +int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu) { struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu); int i; @@ -1984,26 +1981,27 @@ static u64 kvm_hv_send_ipi(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc) return HV_STATUS_SUCCESS; } -void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu) +void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu, bool hyperv_enabled) { + struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu); struct kvm_cpuid_entry2 *entry; - struct kvm_vcpu_hv *hv_vcpu; - entry = kvm_find_cpuid_entry(vcpu, HYPERV_CPUID_INTERFACE); - if (entry && entry->eax == HYPERV_CPUID_SIGNATURE_EAX) { - vcpu->arch.hyperv_enabled = true; - } else { - vcpu->arch.hyperv_enabled = false; - return; - } + vcpu->arch.hyperv_enabled = hyperv_enabled; - if (kvm_hv_vcpu_init(vcpu)) + if (!hv_vcpu) { + /* + * KVM should have already allocated kvm_vcpu_hv if Hyper-V is + * enabled in CPUID. + */ + WARN_ON_ONCE(vcpu->arch.hyperv_enabled); return; - - hv_vcpu = to_hv_vcpu(vcpu); + } memset(&hv_vcpu->cpuid_cache, 0, sizeof(hv_vcpu->cpuid_cache)); + if (!vcpu->arch.hyperv_enabled) + return; + entry = kvm_find_cpuid_entry(vcpu, HYPERV_CPUID_FEATURES); if (entry) { hv_vcpu->cpuid_cache.features_eax = entry->eax; diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h index da2737f2a956..1030b1b50552 100644 --- a/arch/x86/kvm/hyperv.h +++ b/arch/x86/kvm/hyperv.h @@ -23,6 +23,9 @@ #include <linux/kvm_host.h> +/* "Hv#1" signature */ +#define HYPERV_CPUID_SIGNATURE_EAX 0x31237648 + /* * The #defines related to the synthetic debugger are required by KDNet, but * they are not documented in the Hyper-V TLFS because the synthetic debugger @@ -141,7 +144,8 @@ void kvm_hv_request_tsc_page_update(struct kvm *kvm); void kvm_hv_init_vm(struct kvm *kvm); void kvm_hv_destroy_vm(struct kvm *kvm); -void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu); +int kvm_hv_vcpu_init(struct kvm_vcpu *vcpu); +void kvm_hv_set_cpuid(struct kvm_vcpu *vcpu, bool hyperv_enabled); int kvm_hv_set_enforce_cpuid(struct kvm_vcpu *vcpu, bool enforce); int kvm_vm_ioctl_hv_eventfd(struct kvm *kvm, struct kvm_hyperv_eventfd *args); int kvm_get_hv_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid, -- 2.37.2