[PATCH 33/45] KVM: x86: Allow page fault fixup to return errors

[Paolo Bonzini]

kvm_fixup_and_inject_pf_error() reflects intercepted hardware page
faults into the guest, walking the guest page tables when necessary
to obtain an error code consistent with the guest's paging rules.
For example, a GPA that exceeds guest.MAXPHYADDR but fits within
host.MAXPHYADDR must cause a reserved-bit fault, even though hardware
does not report one.

Allow the function's callers to propagate memory attribute failures
from the page table walk; subsequent changes will return from
kvm_fixup_and_inject_pf_error() any error from the page-table walk.

Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/kvm/vmx/vmx.c | 15 +++++++++++----
 arch/x86/kvm/x86.c     |  3 ++-
 arch/x86/kvm/x86.h     |  2 +-
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 27cb0d64fb5c..c4511f83d59b 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5418,10 +5418,14 @@ static int vmx_handle_page_fault(struct kvm_vcpu *vcpu, u32 error_code)
 		WARN_ON_ONCE(!IS_ENABLED(CONFIG_X86_SGX_KVM) ||
 			     !cpu_feature_enabled(X86_FEATURE_SGX2));
 
-		if (guest_cpu_cap_has(vcpu, X86_FEATURE_SGX2))
-			kvm_fixup_and_inject_pf_error(vcpu, cr2, error_code);
-		else
+		if (guest_cpu_cap_has(vcpu, X86_FEATURE_SGX2)) {
+			int r = kvm_fixup_and_inject_pf_error(vcpu, cr2, error_code);
+
+			if (r)
+				return r;
+		} else {
 			kvm_inject_gp(vcpu, 0);
+		}
 		return 1;
 	}
 
@@ -5431,7 +5435,10 @@ static int vmx_handle_page_fault(struct kvm_vcpu *vcpu, u32 error_code)
 	 * to the GPA being legal with respect to host.MAXPHYADDR).
 	 */
 	if (enable_ept) {
-		kvm_fixup_and_inject_pf_error(vcpu, cr2, error_code);
+		int r = kvm_fixup_and_inject_pf_error(vcpu, cr2, error_code);
+
+		if (r)
+			return r;
 		return 1;
 	}
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5818101d1d8a..bb36ca1106e5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10811,7 +10811,7 @@ void kvm_arch_gmem_invalidate_range(struct kvm *kvm, struct kvm_gfn_range *range
 #endif
 #endif
 
-void kvm_fixup_and_inject_pf_error(struct kvm_vcpu *vcpu, gva_t gva, u16 error_code)
+int kvm_fixup_and_inject_pf_error(struct kvm_vcpu *vcpu, gva_t gva, u16 error_code)
 {
 	struct kvm_pagewalk *gva_walk = &vcpu->arch.gva_walk;
 	struct x86_exception fault;
@@ -10833,6 +10833,7 @@ void kvm_fixup_and_inject_pf_error(struct kvm_vcpu *vcpu, gva_t gva, u16 error_c
 		fault.async_page_fault = false;
 	}
 	gva_walk->inject_page_fault(vcpu, &fault, true);
+	return 0;
 }
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_fixup_and_inject_pf_error);
 
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index cfe96962a4e4..4239765629b0 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -368,7 +368,7 @@ void kvm_deliver_exception_payload(struct kvm_vcpu *vcpu,
 				   struct kvm_queued_exception *ex);
 void kvm_handle_exception_payload_quirk(struct kvm_vcpu *vcpu);
 
-void kvm_fixup_and_inject_pf_error(struct kvm_vcpu *vcpu, gva_t gva, u16 error_code);
+int kvm_fixup_and_inject_pf_error(struct kvm_vcpu *vcpu, gva_t gva, u16 error_code);
 int x86_decode_emulated_instruction(struct kvm_vcpu *vcpu, int emulation_type,
 				    void *insn, int insn_len);
 int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
-- 
2.52.0