[PATCH v12 09/11] x86: spp: Add SPP protection check in instruction emulation

[Yang Weijiang]

In instruction/mmio emulation cases, if the target write memroy
is SPP protected, "fake" an vmexit to userspace to let application
handle it.

Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
 arch/x86/kvm/x86.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4b033a39d6c3..e3999a3ab911 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5788,6 +5788,37 @@ 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, gfn_start, gfn_end;
+	struct kvm *kvm = vcpu->kvm;
+	struct kvm_memory_slot *slot;
+	u32 *access;
+
+	if (!kvm->arch.spp_active)
+		return false;
+
+	gfn_start = gpa_to_gfn(gpa);
+	gfn_end = gpa_to_gfn(gpa + bytes);
+	for (gfn = gfn_start; gfn <= gfn_end; gfn++) {
+		slot = gfn_to_memslot(kvm, gfn);
+		if (slot) {
+			access = gfn_to_subpage_wp_info(slot, gfn);
+			if (access && *access != FULL_SPP_ACCESS) {
+				vcpu->run->exit_reason = KVM_EXIT_SPP;
+				vcpu->run->spp.addr = gfn;
+				vcpu->run->spp.insn_len =
+					kvm_x86_ops.get_insn_len(vcpu);
+				return true;
+			}
+		}
+	}
+
+	return false;
+}
+
 static int emulator_read_write_onepage(unsigned long addr, void *val,
 				       unsigned int bytes,
 				       struct x86_exception *exception,
@@ -5817,6 +5848,9 @@ 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;
 
@@ -6963,6 +6997,9 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 		return 1;
 
 	if (r == EMULATION_FAILED) {
+		if (vcpu->run->exit_reason == KVM_EXIT_SPP)
+			return 0;
+
 		if (reexecute_instruction(vcpu, cr2_or_gpa, write_fault_to_spt,
 					emulation_type))
 			return 1;
-- 
2.17.2