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Date:   Thu, 25 May 2023 22:10:15 -0700
From:   Nicolin Chen <nicolinc@nvidia.com>
To:     zhangfei gao <zhangfei.gao@linaro.org>
CC:     <jgg@nvidia.com>, <robin.murphy@arm.com>, <will@kernel.org>,
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        <linux-kernel@vger.kernel.org>, <kvm@vger.kernel.org>,
        <alex.williamson@redhat.com>, <yi.l.liu@intel.com>
Subject: Re: [PATCH v2 00/17] Add Nested Translation Support for SMMUv3
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On Fri, May 26, 2023 at 09:58:52AM +0800, zhangfei gao wrote:

> > I have found two missing pieces in the device detach routine.
> > Applying the following should fix the crash at hotplug path.
> > 
> > ----------------------------------------------------------------------------
> > diff --git a/hw/vfio/container-base.c b/hw/vfio/container-base.c
> > index 89a256efa999..2344307523cb 100644
> > --- a/hw/vfio/container-base.c
> > +++ b/hw/vfio/container-base.c
> > @@ -151,8 +151,10 @@ void vfio_container_destroy(VFIOContainer *container)
> >       }
> > 
> >       QLIST_FOREACH_SAFE(giommu, &container->giommu_list, giommu_next, tmp) {
> > -        memory_region_unregister_iommu_notifier(
> > -                MEMORY_REGION(giommu->iommu_mr), &giommu->n);
> > +        if (giommu->n.notifier_flags) {
> > +            memory_region_unregister_iommu_notifier(
> > +                    MEMORY_REGION(giommu->iommu_mr), &giommu->n);
> > +        }
> >           QLIST_REMOVE(giommu, giommu_next);
> >           g_free(giommu);
> >       }
> > diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
> > index 844c60892db2..35d31480390d 100644
> > --- a/hw/vfio/iommufd.c
> > +++ b/hw/vfio/iommufd.c
> > @@ -652,6 +652,9 @@ found:
> >        */
> >       if (QLIST_EMPTY(&container->hwpt_list)) {
> >           vfio_as_del_container(space, bcontainer);
> > +        if (bcontainer->nested) {
> > +            memory_listener_unregister(& bcontainer->prereg_listener);
> > +        }
> >       }
> >       __vfio_device_detach_container(vbasedev, container, &err);
> >       if (err) {
> > ----------------------------------------------------------------------------
> > 
> > Would you please try your case with it?
> 
> 
> Yes, this solve the hotplug segmentation fault

Nice. Thanks!

> Still report
> 
> qemu-system-aarch64: IOMMU_IOAS_UNMAP failed: No such file or directory
> qemu-system-aarch64: vfio_container_dma_unmap(0xaaaae622e300,
> 0x8000000000, 0x10000) = -2 (No such file or directory)
> qemu-system-aarch64: Failed to unset data -1 (only the first time of
> device_del)
> 
> Test with device_del and device_add

I found the "pci.1" has secondary bus number 0 when VM inits:

(qemu) info pci
  [...]
  Bus  0, device   2, function 0:
    PCI bridge: PCI device 1b36:000c
      IRQ 0, pin A
      BUS 0.
      secondary bus 0.
      subordinate bus 0.
      IO range [0xf000, 0x0fff]
      memory range [0xfff00000, 0x000fffff]
      prefetchable memory range [0xfff00000, 0x000fffff]
      BAR0: 32 bit memory at 0xffffffffffffffff [0x00000ffe].
      id "pci.1"

Then it changes later during the guest OS boots:

(qemu) info pci
  [...]
  Bus  0, device   2, function 0:
    PCI bridge: PCI device 1b36:000c
      IRQ 255, pin A
      BUS 0.
      secondary bus 1.
      subordinate bus 1.
      IO range [0x0000, 0x0fff]
      memory range [0x10000000, 0x101fffff]
      prefetchable memory range [0x8000000000, 0x80000fffff]
      BAR0: 32 bit memory at 0x10240000 [0x10240fff].
      id "pci.1"

This must be related the PCI bus init thing, since it doesn't
fully assign correct the bus numbers and ranges being listed
above, in the first dump.

I will try figuring out what's going on, because this doesn't
make too much sense for our ->set_iommu_device callback if a
PCIBus isn't fully ready.

Alternatively, I could move the set_dev_data ioctl out of the
->set_iommu_device callback to a later stage.

Overall, this should be fixed in the next version.

Thank you
Nicolin