On Thu, Feb 06, 2025 at 09:59:58AM +0100, Eric Auger wrote: > Hi, > > On 2/4/25 12:46 PM, Eric Auger wrote: > > 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? > gentle ping. I am on vacation this week. Will try to get around to it next week. -- Kiryl Shutsemau / Kirill A. Shutemov
