Currently we call kvm_handle_mmio_return when we need to sync back
register content into the guest after a trap.
This function expects its arguments packaged into struct kvm_run,
which we only naturally use when we emulate in userspace. With
in-kernel emulation we have to copy the data into that strcut.
This patch fixes this by explicitly passing the required variables,
so we save the copying in two cases.
Also since this function is actually a NOP for an MMIO write, we
rename it to kvm_writeback_mmio_data and move the !is_write check to
the callers.
This fixes a bug where we were missing a writeback for one in-kernel
emulation case.
Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
---
Hi Christoffer,
this is my take on fixing the missing MMIO writeback call.
This rework kind of hides the actual bug-fix, that's why I dumped
it in favour of the one-liner in my series.
Cheers,
Andre.
arch/arm/include/asm/kvm_mmio.h | 3 ++-
arch/arm/kvm/arm.c | 10 +++++---
arch/arm/kvm/mmio.c | 54 ++++++++++++++++++---------------------
arch/arm64/include/asm/kvm_mmio.h | 3 ++-
virt/kvm/arm/vgic.c | 8 ++----
5 files changed, 38 insertions(+), 40 deletions(-)
diff --git a/arch/arm/include/asm/kvm_mmio.h b/arch/arm/include/asm/kvm_mmio.h
index d8e90c8..21f97ac 100644
--- a/arch/arm/include/asm/kvm_mmio.h
+++ b/arch/arm/include/asm/kvm_mmio.h
@@ -28,7 +28,8 @@ struct kvm_decode {
bool sign_extend;
};
-int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run);
+int kvm_writeback_mmio_data(struct kvm_vcpu *vcpu, void *data, int len,
+ gpa_t addr);
int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
phys_addr_t fault_ipa);
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index b538431..e9f593c 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -555,9 +555,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
return ret;
if (run->exit_reason == KVM_EXIT_MMIO) {
- ret = kvm_handle_mmio_return(vcpu, vcpu->run);
- if (ret)
- return ret;
+ if (!run->mmio.is_write) {
+ ret = kvm_writeback_mmio_data(vcpu, run->mmio.data,
+ run->mmio.len,
+ run->mmio.phys_addr);
+ if (ret)
+ return ret;
+ }
}
if (vcpu->sigset_active)
diff --git a/arch/arm/kvm/mmio.c b/arch/arm/kvm/mmio.c
index 0f6600f..052aa02 100644
--- a/arch/arm/kvm/mmio.c
+++ b/arch/arm/kvm/mmio.c
@@ -86,38 +86,33 @@ static unsigned long mmio_read_buf(char *buf, unsigned int len)
}
/**
- * kvm_handle_mmio_return -- Handle MMIO loads after user space emulation
+ * kvm_writeback_mmio_data -- Write back emulation data into the guest's
+ * target register after return from userspace.
* @vcpu: The VCPU pointer
- * @run: The VCPU run struct containing the mmio data
+ * @data: A pointer to the data to be written back
+ * @len: The size of the read access
+ * @addr: The original MMIO address (for the tracepoint only)
*
* This should only be called after returning from userspace for MMIO load
* emulation.
*/
-int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
+int kvm_writeback_mmio_data(struct kvm_vcpu *vcpu, void *data_ptr, int len,
+ gpa_t addr)
{
unsigned long data;
- unsigned int len;
int mask;
- if (!run->mmio.is_write) {
- len = run->mmio.len;
- if (len > sizeof(unsigned long))
- return -EINVAL;
+ data = mmio_read_buf(data_ptr, len);
- data = mmio_read_buf(run->mmio.data, len);
-
- if (vcpu->arch.mmio_decode.sign_extend &&
- len < sizeof(unsigned long)) {
- mask = 1U << ((len * 8) - 1);
- data = (data ^ mask) - mask;
- }
-
- trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
- data);
- data = vcpu_data_host_to_guest(vcpu, data, len);
- vcpu_set_reg(vcpu, vcpu->arch.mmio_decode.rt, data);
+ if (vcpu->arch.mmio_decode.sign_extend && len < sizeof(unsigned long)) {
+ mask = 1U << ((len * 8) - 1);
+ data = (data ^ mask) - mask;
}
+ trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, addr, data);
+ data = vcpu_data_host_to_guest(vcpu, data, len);
+ vcpu_set_reg(vcpu, vcpu->arch.mmio_decode.rt, data);
+
return 0;
}
@@ -202,22 +197,23 @@ int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
data_buf);
}
+ if (!ret) {
+ /* We handled the access successfully in the kernel. */
+ vcpu->stat.mmio_exit_kernel++;
+ if (!is_write)
+ kvm_writeback_mmio_data(vcpu, data_buf, len, fault_ipa);
+ return 1;
+ }
+
/* Now prepare kvm_run for the potential return to userland. */
run->mmio.is_write = is_write;
run->mmio.phys_addr = fault_ipa;
run->mmio.len = len;
+ run->exit_reason = KVM_EXIT_MMIO;
if (is_write)
memcpy(run->mmio.data, data_buf, len);
- if (!ret) {
- /* We handled the access successfully in the kernel. */
- vcpu->stat.mmio_exit_kernel++;
- kvm_handle_mmio_return(vcpu, run);
- return 1;
- } else {
- vcpu->stat.mmio_exit_user++;
- }
+ vcpu->stat.mmio_exit_user++;
- run->exit_reason = KVM_EXIT_MMIO;
return 0;
}
diff --git a/arch/arm64/include/asm/kvm_mmio.h b/arch/arm64/include/asm/kvm_mmio.h
index fe612a9..00a57bd 100644
--- a/arch/arm64/include/asm/kvm_mmio.h
+++ b/arch/arm64/include/asm/kvm_mmio.h
@@ -30,7 +30,8 @@ struct kvm_decode {
bool sign_extend;
};
-int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run);
+int kvm_writeback_mmio_data(struct kvm_vcpu *vcpu, void *data, int len,
+ gpa_t addr);
int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
phys_addr_t fault_ipa);
diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index 00429b3..7a9aa56 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c
@@ -821,7 +821,6 @@ static int vgic_handle_mmio_access(struct kvm_vcpu *vcpu,
struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
struct vgic_io_device *iodev = container_of(this,
struct vgic_io_device, dev);
- struct kvm_run *run = vcpu->run;
const struct vgic_io_range *range;
struct kvm_exit_mmio mmio;
bool updated_state;
@@ -850,12 +849,9 @@ static int vgic_handle_mmio_access(struct kvm_vcpu *vcpu,
updated_state = false;
}
spin_unlock(&dist->lock);
- run->mmio.is_write = is_write;
- run->mmio.len = len;
- run->mmio.phys_addr = addr;
- memcpy(run->mmio.data, val, len);
- kvm_handle_mmio_return(vcpu, run);
+ if (!is_write)
+ kvm_writeback_mmio_data(vcpu, val, len, addr);
if (updated_state)
vgic_kick_vcpus(vcpu->kvm);
--
2.7.3
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