[RFC PATCH 21/27] KVM: x86: Make kvm_vcpu_after_set_cpuid() return an error code

[Binbin Wu <binbin.wu@linux.intel.com>]

Change kvm_vcpu_after_set_cpuid() to return an error code, in
preparation for adding CPUID paranoid verification that will reject
invalid userspace CPUID configurations.

Have kvm_set_cpuid() check the return value and unwind on failure,
utilizing the existing error path that restores the vCPU's previous
CPUID entries and capabilities.

No functional change intended.

Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
---
 arch/x86/kvm/cpuid.c | 8 ++++++--
 arch/x86/kvm/cpuid.h | 2 +-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 789ec9eb7aaf..08f5bc1d26b1 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -449,7 +449,7 @@ static bool __maybe_unused is_cpuid_subleaf_common_pattern(u32 func, u32 *index)
 	}
 }
 
-void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
+int kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 {
 	u8 cpuid_overlay = get_cpuid_overlay(vcpu->kvm);
 	struct kvm_lapic *apic = vcpu->arch.apic;
@@ -543,6 +543,8 @@ void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 	kvm_mmu_after_set_cpuid(vcpu);
 
 	kvm_make_request(KVM_REQ_RECALC_INTERCEPTS, vcpu);
+
+	return 0;
 }
 
 int cpuid_query_maxphyaddr(struct kvm_vcpu *vcpu)
@@ -649,7 +651,9 @@ static int kvm_set_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *e2,
 #ifdef CONFIG_KVM_XEN
 	vcpu->arch.xen.cpuid = kvm_get_hypervisor_cpuid(vcpu, XEN_SIGNATURE);
 #endif
-	kvm_vcpu_after_set_cpuid(vcpu);
+	r = kvm_vcpu_after_set_cpuid(vcpu);
+	if (r)
+		goto err;
 
 success:
 	kvfree(e2);
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index 535377e519b5..cff5e71579ce 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -42,7 +42,7 @@ static inline void kvm_finalize_cpu_caps(void)
 	kvm_is_configuring_cpu_caps = false;
 }
 
-void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu);
+int kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu);
 struct kvm_cpuid_entry2 *kvm_find_cpuid_entry2(struct kvm_cpuid_entry2 *entries,
 					       int nent, u32 function, u64 index);
 /*
-- 
2.46.0