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KVM: x86: Report error when setting CPUID if Hyper-V allocation fails

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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: 10d7bf1e46 ("KVM: x86: hyper-v: Cache guest CPUID leaves determining features availability")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220830133737.1539624-6-vkuznets@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2022-08-30 15:37:09 +02:00 committed by Paolo Bonzini
parent 1cac8d9f6b
commit 3be29eb7b5
3 changed files with 36 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
arch/x86/kvm/cpuid.c
View File

@ -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;

30
arch/x86/kvm/hyperv.c
View File

@ -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 @@ ret_success:
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;
vcpu->arch.hyperv_enabled = hyperv_enabled;
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;
}
if (kvm_hv_vcpu_init(vcpu))
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;

6
arch/x86/kvm/hyperv.h
View File

@ -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,