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Tsirkin" Cc: Eric Auger , "Kirill A. Shutemov" , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Zhenzhong Duan , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org References: <20240808075141.3433253-1-kirill.shutemov@linux.intel.com> <20250203094700-mutt-send-email-mst@kernel.org> <7cee3c9e-515e-41de-a15c-04c7591e83eb@redhat.com> <6bce0f4c-636f-456b-ab21-4a25d3dc8803@redhat.com> <90a09ffa-e316-41f0-916b-25635b1d4bc6@linux.intel.com> <83b43e73-8599-44ff-8657-6d5f2f9b2de5@redhat.com> <20250214070904-mutt-send-email-mst@kernel.org> <20250217191103-mutt-send-email-mst@kernel.org> Content-Language: en-US From: "Ning, Hongyu" In-Reply-To: <20250217191103-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2025/2/18 8:12, Michael S. Tsirkin wrote: > On Tue, Feb 18, 2025 at 07:57:23AM +0800, Ning, Hongyu wrote: >> >> >> On 2025/2/17 17:25, 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 >>>>>>>>>>> Reported-by: Hongyu Ning >>>>>>>>>> >>>>>>>>>> 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/) >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Reviewed-by: Eric Auger >>>>>>>>>> Tested-by: Eric Auger >>>>>>>>>> >>>>>>>>>> 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 assume this still works for you, yes? >>> Would that still been done in the virtio_dev_shutdown()? >>> >>> Is that what you tested Hongyu? >> >> Hi Eric, >> >> my patch applied based on Michael's comments: >> >> --- >> drivers/virtio/virtio.c | 20 ++++++++++++++++++++ >> 1 file changed, 20 insertions(+) >> >> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c >> index ba37665188b5..458dc28be060 100644 >> --- a/drivers/virtio/virtio.c >> +++ b/drivers/virtio/virtio.c >> @@ -395,6 +395,25 @@ 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); >> + /* >> + * 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); >> + //virtio_reset_device(dev); >> +} >> + >> static const struct bus_type virtio_bus = { >> .name = "virtio", >> .match = virtio_dev_match, >> @@ -403,6 +422,7 @@ 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 > > > > yes, that's the patch. Does it work for you? Addresses the > problem? If yes I'll repost. > yes, issue fixed on my side. Thanks. >> >>> >>> 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) >>>>>>>>> >>>>>>>> >>>>>>> >>>>>> >>>> >>> >>> > >