[PATCH v6 9/9] x86: spp: Add SPP protection check in emulation.

[Yang Weijiang <weijiang.yang@xxxxxxxxx>]

In instruction/mmio emulation cases, if the target write memroy
is SPP protected, exit to user-space to handle it as if it's
caused by SPP induced EPT violation due to guest write.

Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
 arch/x86/kvm/x86.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fa114b5db672..71f5a8ae76cf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5525,6 +5525,36 @@ static const struct read_write_emulator_ops write_emultor = {
 	.write = true,
 };
 
+static bool is_emulator_spp_protected(struct kvm_vcpu *vcpu,
+				      gpa_t gpa,
+				      unsigned int bytes)
+{
+	gfn_t gfn, start_gfn, end_gfn;
+	struct kvm *kvm = vcpu->kvm;
+	struct kvm_memory_slot *slot;
+	u32 access;
+
+	if (!kvm->arch.spp_active)
+		return false;
+
+	start_gfn = gpa >> PAGE_SHIFT;
+	end_gfn = (gpa + bytes) >> PAGE_SHIFT;
+	for (gfn = start_gfn; gfn <= end_gfn; gfn++) {
+		slot = gfn_to_memslot(kvm, gfn);
+		if (slot) {
+			access = *gfn_to_subpage_wp_info(slot, gfn);
+			if (access != FULL_SPP_ACCESS) {
+				vcpu->run->exit_reason = KVM_EXIT_SPP;
+				vcpu->run->spp.addr = gfn;
+				kvm_skip_emulated_instruction(vcpu);
+				return true;
+			}
+		}
+	}
+
+	return false;
+}
+
 static int emulator_read_write_onepage(unsigned long addr, void *val,
 				       unsigned int bytes,
 				       struct x86_exception *exception,
@@ -5555,6 +5585,9 @@ static int emulator_read_write_onepage(unsigned long addr, void *val,
 			return X86EMUL_PROPAGATE_FAULT;
 	}
 
+	if (write && is_emulator_spp_protected(vcpu, gpa, bytes))
+		return X86EMUL_UNHANDLEABLE;
+
 	if (!ret && ops->read_write_emulate(vcpu, gpa, val, bytes))
 		return X86EMUL_CONTINUE;
 
@@ -6616,6 +6649,9 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
 		return EMULATE_DONE;
 
 	if (r == EMULATION_FAILED) {
+		if (vcpu->run->exit_reason == KVM_EXIT_SPP)
+			return EMULATE_USER_EXIT;
+
 		if (reexecute_instruction(vcpu, cr2, write_fault_to_spt,
 					emulation_type))
 			return EMULATE_DONE;
-- 
2.17.2