[PATCH v16 114/116] RFC: KVM: x86: Add x86 callback to check cpuid

[isaku . yamahata]

From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

The x86 backend should check the consistency of KVM_SET_CPUID2 because it
has its constraint.  Add a callback for it.  The backend code will come as
another patch.

Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Link: https://lore.kernel.org/lkml/ZDiGpCkXOcCm074O@xxxxxxxxxx/
Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
---
 arch/x86/include/asm/kvm-x86-ops.h |  2 ++
 arch/x86/include/asm/kvm_host.h    |  1 +
 arch/x86/kvm/cpuid.c               | 20 ++++++++++++--------
 3 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 8b3c5f2179cf..ba74cb7199b3 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -20,6 +20,8 @@ KVM_X86_OP(hardware_disable)
 KVM_X86_OP(hardware_unsetup)
 KVM_X86_OP_OPTIONAL_RET0(offline_cpu)
 KVM_X86_OP(has_emulated_msr)
+/* TODO: Once all backend implemented this op, remove _OPTIONAL_RET0. */
+KVM_X86_OP_OPTIONAL_RET0(vcpu_check_cpuid)
 KVM_X86_OP(vcpu_after_set_cpuid)
 KVM_X86_OP(is_vm_type_supported)
 KVM_X86_OP_OPTIONAL(max_vcpus);
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f0674ef1c17e..8ac6f0555ac3 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1619,6 +1619,7 @@ struct kvm_x86_ops {
 	void (*hardware_unsetup)(void);
 	int (*offline_cpu)(void);
 	bool (*has_emulated_msr)(struct kvm *kvm, u32 index);
+	int (*vcpu_check_cpuid)(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *e2, int nent);
 	void (*vcpu_after_set_cpuid)(struct kvm_vcpu *vcpu);
 
 	bool (*is_vm_type_supported)(unsigned long vm_type);
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index da46f284ec65..7ce2fdba8fff 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -136,6 +136,7 @@ static int kvm_check_cpuid(struct kvm_vcpu *vcpu,
 {
 	struct kvm_cpuid_entry2 *best;
 	u64 xfeatures;
+	int r;
 
 	/*
 	 * The existing code assumes virtual address is 48-bit or 57-bit in the
@@ -155,15 +156,18 @@ static int kvm_check_cpuid(struct kvm_vcpu *vcpu,
 	 * enabling in the FPU, e.g. to expand the guest XSAVE state size.
 	 */
 	best = cpuid_entry2_find(entries, nent, 0xd, 0);
-	if (!best)
-		return 0;
-
-	xfeatures = best->eax | ((u64)best->edx << 32);
-	xfeatures &= XFEATURE_MASK_USER_DYNAMIC;
-	if (!xfeatures)
-		return 0;
+	if (best) {
+		xfeatures = best->eax | ((u64)best->edx << 32);
+		xfeatures &= XFEATURE_MASK_USER_DYNAMIC;
+		if (xfeatures) {
+			r = fpu_enable_guest_xfd_features(&vcpu->arch.guest_fpu,
+							  xfeatures);
+			if (r)
+				return r;
+		}
+	}
 
-	return fpu_enable_guest_xfd_features(&vcpu->arch.guest_fpu, xfeatures);
+	return static_call(kvm_x86_vcpu_check_cpuid)(vcpu, entries, nent);
 }
 
 /* Check whether the supplied CPUID data is equal to what is already set for the vCPU. */
-- 
2.25.1