On 2025/2/6 16:59, Eric Auger wrote:

Hi,

On 2/4/25 12:46 PM, Eric Auger wrote:

quoted

Hi,

On 2/3/25 3:48 PM, Michael S. Tsirkin wrote:

quoted

On Fri, Jan 31, 2025 at 10:53:15AM +0100, Eric Auger wrote:

quoted

Hi Kirill, Michael

On 8/8/24 9:51 AM, Kirill A. Shutemov wrote:

quoted

Hongyu reported a hang on kexec in a VM. QEMU reported invalid memory
accesses during the hang.

	Invalid read at addr 0x102877002, size 2, region '(null)', reason: rejected
	Invalid write at addr 0x102877A44, size 2, region '(null)', reason: rejected
	...

It was traced down to virtio-console. Kexec works fine if virtio-console
is not in use.

Looks like virtio-console continues to write to the MMIO even after
underlying virtio-pci device is removed.

The problem can be mitigated by removing all virtio devices on virtio
bus shutdown.

Signed-off-by: Kirill A. Shutemov <redacted>
Reported-by: Hongyu Ning <redacted>

Gentle ping on that patch that seems to have fallen though the cracks.

I think this fix is really needed. I have another test case with a
rebooting guest exposed with virtio-net (backed by vhost-net) and
viommu. Since there is currently no shutdown for the virtio-net, on
reboot, the IOMMU is disabled through the native_machine_shutdown()/
x86_platform.iommu_shutdown() while the virtio-net is still alive.

Normally device_shutdown() should call virtio-net shutdown before the
IOMMU tear down and we wouldn't see any spurious transactions after
iommu shutdown.

With that fix, the above test case is fixed and I do not see spurious
vhost IOTLB miss spurious requests.

For more details, see qemu thread ([PATCH] hw/virtio/vhost: Disable
IOTLB callbacks when IOMMU gets disabled,
https://lore.kernel.org/all/20250120173339.865681-1-eric.auger@redhat.com/ (local))


Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric

quoted

---
  drivers/virtio/virtio.c | 10 ++++++++++
  1 file changed, 10 insertions(+)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index a9b93e99c23a..6c2f908eb22c 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c

@@ -356,6 +356,15 @@ static void virtio_dev_remove(struct device *_d)
  	of_node_put(dev->dev.of_node);
  }
  
+static void virtio_dev_shutdown(struct device *_d)
+{
+	struct virtio_device *dev = dev_to_virtio(_d);
+	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
+
+	if (drv && drv->remove)
+		drv->remove(dev);

I am concerned that full remove is a heavyweight operation.
Do not want to slow down reboots even more.
How about just doing a reset, instead?

I tested with

static void virtio_dev_shutdown(struct device *_d)
{
         struct virtio_device *dev = dev_to_virtio(_d);

         virtio_reset_device(dev);
}


and it fixes my issue.

Kirill, would that fix you issue too?

Hi,

sorry for my late response, I synced with Kirill offline and did a retest.

The issue is still reproduced on my side, kexec will be stuck in case of 
"console=hvc0" append in kernel cmdline and even with such patch applied.

my kernel code base is 6.14.0-rc2.

let me know if any more experiments needed.

---
  drivers/virtio/virtio.c | 8 ++++++++
  1 file changed, 8 insertions(+)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index ba37665188b5..f9f885d04763 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c

@@ -395,6 +395,13 @@ static const struct cpumask 

*virtio_irq_get_affinity(struct device *_d,
         return dev->config->get_vq_affinity(dev, irq_vec);
  }

+static void virtio_dev_shutdown(struct device *_d)
+{
+        struct virtio_device *dev = dev_to_virtio(_d);
+
+        virtio_reset_device(dev);
+}
+
  static const struct bus_type virtio_bus = {
         .name  = "virtio",
         .match = virtio_dev_match,

@@ -403,6 +410,7 @@ static const struct bus_type virtio_bus = {
         .probe = virtio_dev_probe,
         .remove = virtio_dev_remove,
         .irq_get_affinity = virtio_irq_get_affinity,
+       .shutdown = virtio_dev_shutdown,
  };

  int __register_virtio_driver(struct virtio_driver *driver, struct 

module *owner)
--
2.43.0

gentle ping.

this also fixes another issue with qemu vSMMU + virtio-scsi-pci. With
the above addition I get rid of spurious warning in qemu on guest reboot.

qemu-system-aarch64: virtio: zero sized buffers are not allowed
qemu-system-aarch64: vhost vring error in virtqueue 0: Invalid argument (22)

Would you mind if I respin?

Thanks

Eric

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Thanks

Eric

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quoted

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+}
+
  static const struct bus_type virtio_bus = {
  	.name  = "virtio",
  	.match = virtio_dev_match,

@@ -363,6 +372,7 @@ static const struct bus_type virtio_bus = {
  	.uevent = virtio_uevent,
  	.probe = virtio_dev_probe,
  	.remove = virtio_dev_remove,
+	.shutdown = virtio_dev_shutdown,
  };
  
  int __register_virtio_driver(struct virtio_driver *driver, struct module *owner)