[PATCH 10/10] KVM: indicate readonly access fault

From: Xiao Guangrong
Date: Tue Jul 17 2012 - 10:46:37 EST


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 46e13a1..cc5f8f0 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3703,9 +3703,10 @@ 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 {
@@ -3735,7 +3736,7 @@ 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,
@@ -3797,7 +3798,8 @@ 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:
@@ -3819,6 +3821,7 @@ mmio:
frag->gpa = gpa;
frag->data = val;
frag->len = now;
+ frag->write_readonly_mem = (ret == -EPERM);

gpa += now;
val += now;
@@ -3836,6 +3839,7 @@ 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 a2302e7..7e45014 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -142,6 +142,7 @@ 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 50e18c0..8d4bc55 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1527,6 +1527,9 @@ int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn, const void *data,
unsigned long addr;

addr = gfn_to_hva(kvm, gfn);
+ if (kvm_is_readonly_bad_hva(addr))
+ 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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