KVM: arm/arm64: Fix MMIO emulation data handling

When the kernel was handling a guest MMIO read access internally, we need to copy the emulation result into the run->mmio structure in order for the kvm_handle_mmio_return() function to pick it up and inject the result back into the guest. Currently the only user of kvm_io_bus for ARM is the VGIC, which did this copying itself, so this was not causing issues so far. But with the upcoming new vgic implementation we need this done properly. Update the kvm_handle_mmio_return description and cleanup the code to only perform a single copying when needed. Code and commit message inspired by Andre Przywara. Reported-by: Andre Przywara <[email protected]> Signed-off-by: Christoffer Dall <[email protected]> Signed-off-by: Andre Przywara <[email protected]> Reviewed-by: Marc Zyngier <[email protected]> Reviewed-by: Andre Przywara <[email protected]>
lucamilanesio · May 20, 2016 · 83091db · 83091db
1 parent 2db4c10
commit 83091db
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Showing 2 changed files with 7 additions and 14 deletions.
diff --git a/arch/arm/kvm/mmio.c b/arch/arm/kvm/mmio.c
@@ -87,11 +87,10 @@ static unsigned long mmio_read_buf(char *buf, unsigned int len)
 
 /**
  * kvm_handle_mmio_return -- Handle MMIO loads after user space emulation
+ *			     or in-kernel IO emulation
+ *
  * @vcpu: The VCPU pointer
  * @run:  The VCPU run struct containing the mmio data
- *
- * 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)
 {
@@ -206,18 +205,19 @@ int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
 	run->mmio.is_write	= is_write;
 	run->mmio.phys_addr	= fault_ipa;
 	run->mmio.len		= len;
-	if (is_write)
-		memcpy(run->mmio.data, data_buf, len);
 
 	if (!ret) {
 		/* We handled the access successfully in the kernel. */
+		if (!is_write)
+			memcpy(run->mmio.data, data_buf, len);
 		vcpu->stat.mmio_exit_kernel++;
 		kvm_handle_mmio_return(vcpu, run);
 		return 1;
-	} else {
-		vcpu->stat.mmio_exit_user++;
 	}
 
+	if (is_write)
+		memcpy(run->mmio.data, data_buf, len);
+	vcpu->stat.mmio_exit_user++;
 	run->exit_reason	= KVM_EXIT_MMIO;
 	return 0;
 }
diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
@@ -819,7 +819,6 @@ 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;
@@ -848,12 +847,6 @@ 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 (updated_state)
 		vgic_kick_vcpus(vcpu->kvm);