[PATCH v5 12/12] KVM: indicate readonly access fault

[Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>]

Introduce write_readonly_mem in mmio-exit-info to indicate this exit is
caused by write access on readonly memslot

Signed-off-by: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx>
---
 arch/x86/kvm/x86.c       |   12 ++++++++----
 include/linux/kvm.h      |    3 +++
 include/linux/kvm_host.h |    1 +
 virt/kvm/kvm_main.c      |    3 +++
 4 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8cde327..5e10482 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3704,9 +3704,10 @@ int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,

 	ret = kvm_write_guest(vcpu->kvm, gpa, val, bytes);
 	if (ret < 0)
-		return 0;
+		return ret;
+
 	kvm_mmu_pte_write(vcpu, gpa, val, bytes);
-	return 1;
+	return 0;
 }

 struct read_write_emulator_ops {
@@ -3736,7 +3737,7 @@ static int read_prepare(struct kvm_vcpu *vcpu, void *val, int bytes)
 static int read_emulate(struct kvm_vcpu *vcpu, gpa_t gpa,
 			void *val, int bytes)
 {
-	return !kvm_read_guest(vcpu->kvm, gpa, val, bytes);
+	return kvm_read_guest(vcpu->kvm, gpa, val, bytes);
 }

 static int write_emulate(struct kvm_vcpu *vcpu, gpa_t gpa,
@@ -3798,7 +3799,8 @@ static int emulator_read_write_onepage(unsigned long addr, void *val,
 	if (ret)
 		goto mmio;

-	if (ops->read_write_emulate(vcpu, gpa, val, bytes))
+	ret = ops->read_write_emulate(vcpu, gpa, val, bytes);
+	if (!ret)
 		return X86EMUL_CONTINUE;

 mmio:
@@ -3820,6 +3822,7 @@ mmio:
 		frag->gpa = gpa;
 		frag->data = val;
 		frag->len = now;
+		frag->write_readonly_mem = (ret == -EPERM);

 		gpa += now;
 		val += now;
@@ -3837,6 +3840,7 @@ static void set_mmio_exit_info(struct kvm_vcpu *vcpu,
 	run->mmio.phys_addr = frag->gpa;
 	run->mmio.len = frag->len;
 	run->mmio.is_write = vcpu->mmio_is_write = write;
+	run->mmio.write_readonly_mem = frag->write_readonly_mem;

 	if (write)
 		memcpy(run->mmio.data, frag->data, frag->len);
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 94867d0..9261541 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -222,6 +222,9 @@ struct kvm_run {
 			__u8  data[8];
 			__u32 len;
 			__u8  is_write;
+#ifdef __KVM_HAVE_READONLY_MEM
+			__u8 write_readonly_mem;
+#endif
 		} mmio;
 		/* KVM_EXIT_HYPERCALL */
 		struct {
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 2df6861..c47979d 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -184,6 +184,7 @@ struct kvm_mmio_fragment {
 	gpa_t gpa;
 	void *data;
 	unsigned len;
+	bool write_readonly_mem;
 };

 struct kvm_vcpu {
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 5e899d9..d0babc9 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1445,6 +1445,9 @@ int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn, const void *data,
 	unsigned long addr;

 	addr = gfn_to_hva(kvm, gfn);
+	if (addr == KVM_HVA_ERR_RO_BAD)
+		return -EPERM;
+
 	if (kvm_is_error_hva(addr))
 		return -EFAULT;
 	r = __copy_to_user((void __user *)addr + offset, data, len);
-- 
1.7.7.6

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