[PATCH v7 1/2] KVM: x86/cpuid: generalize kvm_update_kvm_cpuid_base() and also capture limit

From: Paul Durrant
Date: Fri Jan 06 2023 - 05:36:38 EST


A subsequent patch will need to acquire the CPUID leaf range for emulated
Xen so explicitly pass the signature of the hypervisor we're interested in
to the new function. Also introduce a new kvm_hypervisor_cpuid structure
so we can neatly store both the base and limit leaf indices.

Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
---
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>

v7:
- Morph kvm_update_hypervisor_cpuid() into kvm_get_hypervisor_cpuid()
- Place the definition of struct kvm_hypervisor_cpuid to avoid churn
in patch #2.

v6:
- New in this version
---
arch/x86/include/asm/kvm_host.h | 7 ++++++-
arch/x86/kvm/cpuid.c | 24 +++++++++++++-----------
2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c70690b2c82d..85cbe4571ac9 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -678,6 +678,11 @@ struct kvm_vcpu_hv {
} nested;
};

+struct kvm_hypervisor_cpuid {
+ u32 base;
+ u32 limit;
+};
+
/* Xen HVM per vcpu emulation context */
struct kvm_vcpu_xen {
u64 hypercall_rip;
@@ -826,7 +831,7 @@ struct kvm_vcpu_arch {

int cpuid_nent;
struct kvm_cpuid_entry2 *cpuid_entries;
- u32 kvm_cpuid_base;
+ struct kvm_hypervisor_cpuid kvm_cpuid;

u64 reserved_gpa_bits;
int maxphyaddr;
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 69768e4d53a6..db5a4d38fcd0 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -180,15 +180,15 @@ static int kvm_cpuid_check_equal(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2
return 0;
}

-static void kvm_update_kvm_cpuid_base(struct kvm_vcpu *vcpu)
+static struct kvm_hypervisor_cpuid kvm_get_hypervisor_cpuid(struct kvm_vcpu *vcpu,
+ const char *sig)
{
- u32 function;
+ struct kvm_hypervisor_cpuid cpuid = {};
struct kvm_cpuid_entry2 *entry;
+ u32 base;

- vcpu->arch.kvm_cpuid_base = 0;
-
- for_each_possible_hypervisor_cpuid_base(function) {
- entry = kvm_find_cpuid_entry(vcpu, function);
+ for_each_possible_hypervisor_cpuid_base(base) {
+ entry = kvm_find_cpuid_entry(vcpu, base);

if (entry) {
u32 signature[3];
@@ -197,19 +197,21 @@ static void kvm_update_kvm_cpuid_base(struct kvm_vcpu *vcpu)
signature[1] = entry->ecx;
signature[2] = entry->edx;

- BUILD_BUG_ON(sizeof(signature) > sizeof(KVM_SIGNATURE));
- if (!memcmp(signature, KVM_SIGNATURE, sizeof(signature))) {
- vcpu->arch.kvm_cpuid_base = function;
+ if (!memcmp(signature, sig, sizeof(signature))) {
+ cpuid.base = base;
+ cpuid.limit = entry->eax;
break;
}
}
}
+
+ return cpuid;
}

static struct kvm_cpuid_entry2 *__kvm_find_kvm_cpuid_features(struct kvm_vcpu *vcpu,
struct kvm_cpuid_entry2 *entries, int nent)
{
- u32 base = vcpu->arch.kvm_cpuid_base;
+ u32 base = vcpu->arch.kvm_cpuid.base;

if (!base)
return NULL;
@@ -439,7 +441,7 @@ static int kvm_set_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *e2,
vcpu->arch.cpuid_entries = e2;
vcpu->arch.cpuid_nent = nent;

- kvm_update_kvm_cpuid_base(vcpu);
+ vcpu->arch.kvm_cpuid = kvm_get_hypervisor_cpuid(vcpu, KVM_SIGNATURE);
kvm_vcpu_after_set_cpuid(vcpu);

return 0;
--
2.20.1