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

[Paul Durrant <pdurrant@xxxxxxxxxx>]

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