Hi, On 2/3/25 3:48 PM, Michael S. Tsirkin wrote: > On Fri, Jan 31, 2025 at 10:53:15AM +0100, Eric Auger wrote: >> Hi Kirill, Michael >> >> On 8/8/24 9:51 AM, Kirill A. Shutemov wrote: >>> 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 <kirill.shutemov@xxxxxxxxxxxxxxx> >>> Reported-by: Hongyu Ning <hongyu.ning@xxxxxxxxxxxxxxx> >> >> 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@xxxxxxxxxx/) >> >> >> Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx> >> Tested-by: Eric Auger <eric.auger@xxxxxxxxxx> >> >> Thanks >> >> Eric >> >>> --- >>> 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? Thanks Eric > >>> +} >>> + >>> 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) >
