KVM: x86: disconnect kvm_check_cpuid() from vcpu->arch.cpuid_entries

As a preparatory step to allocating vcpu->arch.cpuid_entries dynamically
make kvm_check_cpuid() check work with an arbitrary 'struct kvm_cpuid_entry2'
array.

Currently, when kvm_check_cpuid() fails we reset vcpu->arch.cpuid_nent to
0 and this is kind of weird, i.e. one would expect CPUIDs to remain
unchanged when KVM_SET_CPUID[2] call fails.

No functional change intended. It would've been possible to move the updated
kvm_check_cpuid() in kvm_vcpu_ioctl_set_cpuid2() and check the supplied
input before we start updating vcpu->arch.cpuid_entries/nent but we
can't do the same in kvm_vcpu_ioctl_set_cpuid() as we'll have to copy
'struct kvm_cpuid_entry' entries first. The change will be made when
vcpu->arch.cpuid_entries[] array becomes allocated dynamically.

Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20201001130541.1398392-2-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index d253c02..2e4228c 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -54,7 +54,24 @@ static u32 xstate_required_size(u64 xstate_bv, bool compacted)
 
 #define F feature_bit
 
-static int kvm_check_cpuid(struct kvm_vcpu *vcpu)
+static inline struct kvm_cpuid_entry2 *cpuid_entry2_find(
+       struct kvm_cpuid_entry2 *entries, int nent, u32 function, u32 index)
+{
+       struct kvm_cpuid_entry2 *e;
+       int i;
+
+       for (i = 0; i < nent; i++) {
+               e = &entries[i];
+
+               if (e->function == function && (e->index == index ||
+                   !(e->flags & KVM_CPUID_FLAG_SIGNIFCANT_INDEX)))
+                       return e;
+       }
+
+       return NULL;
+}
+
+static int kvm_check_cpuid(struct kvm_cpuid_entry2 *entries, int nent)
 {
        struct kvm_cpuid_entry2 *best;
 
@@ -62,7 +79,7 @@ static int kvm_check_cpuid(struct kvm_vcpu *vcpu)
         * The existing code assumes virtual address is 48-bit or 57-bit in the
         * canonical address checks; exit if it is ever changed.
         */
-       best = kvm_find_cpuid_entry(vcpu, 0x80000008, 0);
+       best = cpuid_entry2_find(entries, nent, 0x80000008, 0);
        if (best) {
                int vaddr_bits = (best->eax & 0xff00) >> 8;
 
@@ -227,7 +244,7 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
                vcpu->arch.cpuid_entries[i].padding[2] = 0;
        }
        vcpu->arch.cpuid_nent = cpuid->nent;
-       r = kvm_check_cpuid(vcpu);
+       r = kvm_check_cpuid(vcpu->arch.cpuid_entries, cpuid->nent);
        if (r) {
                vcpu->arch.cpuid_nent = 0;
                kvfree(cpuid_entries);
@@ -257,7 +274,7 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
                           cpuid->nent * sizeof(struct kvm_cpuid_entry2)))
                goto out;
        vcpu->arch.cpuid_nent = cpuid->nent;
-       r = kvm_check_cpuid(vcpu);
+       r = kvm_check_cpuid(vcpu->arch.cpuid_entries, cpuid->nent);
        if (r) {
                vcpu->arch.cpuid_nent = 0;
                goto out;
@@ -947,17 +964,8 @@ out_free:
 struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
                                              u32 function, u32 index)
 {
-       struct kvm_cpuid_entry2 *e;
-       int i;
-
-       for (i = 0; i < vcpu->arch.cpuid_nent; ++i) {
-               e = &vcpu->arch.cpuid_entries[i];
-
-               if (e->function == function && (e->index == index ||
-                   !(e->flags & KVM_CPUID_FLAG_SIGNIFCANT_INDEX)))
-                       return e;
-       }
-       return NULL;
+       return cpuid_entry2_find(vcpu->arch.cpuid_entries, vcpu->arch.cpuid_nent,
+                                function, index);
 }
 EXPORT_SYMBOL_GPL(kvm_find_cpuid_entry);