From 3be29eb7b5251a772e2033761a9b67981fdfb0f7 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 30 Aug 2022 15:37:09 +0200 Subject: KVM: x86: Report error when setting CPUID if Hyper-V allocation fails 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 Signed-off-by: Vitaly Kuznetsov Signed-off-by: Sean Christopherson Link: https://lore.kernel.org/r/20220830133737.1539624-6-vkuznets@redhat.com Signed-off-by: Paolo Bonzini --- arch/x86/kvm/cpuid.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) (limited to 'arch/x86/kvm/cpuid.c') 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; -- cgit v1.2.3