On Mon, Feb 17, 2025 at 05:59:30PM +0100, Eric Auger wrote: > Hi Michael, > > On 2/17/25 10:25 AM, Eric Auger wrote: > > Hi Michael, Hongyu, > > > > On 2/14/25 1:16 PM, Michael S. Tsirkin wrote: > >> On Fri, Feb 14, 2025 at 08:56:56AM +0100, Eric Auger wrote: > >>> Hi, > >>> > >>> On 2/14/25 8:21 AM, Ning, Hongyu wrote: > >>>> > >>>> > >>>> On 2025/2/6 16:59, 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? > >>>> > >>>> 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. > >>> > >>> Thanks for testing! > >>> > >>> Michael, it looks like the initial patch from Kyrill is the one that > >>> fixes both issues. virtio_reset_device() usage does not work for the > >>> initial bug report while it works for me. Other ideas? > >>> > >>> Thanks > >>> > >>> Eric > >> > >> Ah, wait a second. > >> > >> Looks like virtio-console continues to write to the MMIO even after > >> underlying virtio-pci device is removed. > >> > >> Hmm. I am not sure why that is a problem, but I assume some hypervisors just > >> hang the system if you try to kick them after reset. > >> Unfortunate that spec did not disallow it. > >> > >> If we want to prevent that, we want to do something like this: > >> > >> > >> /* > >> * Some devices get wedged if you kick them after they are > >> * reset. Mark all vqs as broken to make sure we don't. > >> */ > >> virtio_break_device(dev); > >> /* > >> * The below virtio_synchronize_cbs() guarantees that any > >> * interrupt for this line arriving after > >> * virtio_synchronize_vqs() has completed is guaranteed to see > >> * vq->broken as true. > >> */ > >> virtio_synchronize_cbs(dev); > >> dev->config->reset(dev); > I have tested that code as an implentation of the virtio shutdown > callback and yes it also fixes the viommu/vhost issue. > > Michael, will you send a patch then? > > Thanks > > Eric Was hoping for a confirmation from Ning. > >> > >> > >> I assume this still works for you, yes? > > Would that still been done in the virtio_dev_shutdown()? > > > > Is that what you tested Hongyu? > > > > Eric > >> > >> > >> > >>>> > >>>> 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 > >>>>> > >>>>> > >>>>> > >>>>> > >>>>>> > >>>>>> 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) > >>>>>>> > >>>>>> > >>>>> > >>>> > >> > >
