Re: [Qemu-devel] [PATCH v2 0/3] ivshmem: MSI bug fixes

[Ladi Prosek]

On Mon, Nov 20, 2017 at 1:49 PM, Ladi Prosek <address@hidden> wrote:
> On Mon, Nov 20, 2017 at 10:07 AM, Ladi Prosek <address@hidden> wrote:
>> On Sun, Nov 19, 2017 at 9:39 PM,  <address@hidden> wrote:
>>> I just updated to the latest build and applied this patch set, now on VM
>>> reset the qemu crashes with the following assert:
>>>
>>> ivshmem.c:467: ivshmem_add_kvm_msi_virq: Assertion
>>> `!s->msi_vectors[vector].pdev' failed.
>>
>> I see asserts too. Even with v1 on top of QEMU v2.10.0 so I must have
>> missed something.
>>
>> Looking. And, needless to say, these patches should not be applied just yet 
>> :)
>
> Ok, here goes it.
>
> 1)
> ivshmem.c:467: ivshmem_add_kvm_msi_virq: Assertion
> `!s->msi_vectors[vector].pdev' failed.
>
> Is caused by the ivshmem device not undoing the effects of
> ivshmem_enable_irqfd() on reset.
>
> This fix works for me:
>
> --- a/hw/misc/ivshmem.c
> +++ b/hw/misc/ivshmem.c
> @@ -758,10 +758,15 @@ static void ivshmem_msix_vector_use(IVShmemState *s)
>      }
>  }
>
> +
> +static void ivshmem_disable_irqfd(IVShmemState *s);
> +
>  static void ivshmem_reset(DeviceState *d)
>  {
>      IVShmemState *s = IVSHMEM_COMMON(d);
>
> +    ivshmem_disable_irqfd(s);
> +
>      s->intrstatus = 0;
>      s->intrmask = 0;
>      if (ivshmem_has_feature(s, IVSHMEM_MSI)) {

I have added this to v3 as patch 4.

> 2)
> ivshmem.c:354: ivshmem_vector_mask: Assertion `v->unmasked' failed.
>
> which I've been also getting after I enabled Driver Verifier and
> Windows started crashing
> (https://github.com/virtio-win/kvm-guest-drivers-windows/pull/199), is
> caused by the MSI-X code masking already masked vectors on reset. I'm
> going to post a patch similar to this:
>
> --- a/hw/pci/msix.c
> +++ b/hw/pci/msix.c
> @@ -500,11 +500,12 @@ void msix_reset(PCIDevice *dev)
>          return;
>      }
>      msix_clear_all_vectors(dev);
> +    msix_mask_all(dev, dev->msix_entries_nr);
>      dev->config[dev->msix_cap + MSIX_CONTROL_OFFSET] &=
>             ~dev->wmask[dev->msix_cap + MSIX_CONTROL_OFFSET];
>      memset(dev->msix_table, 0, dev->msix_entries_nr * PCI_MSIX_ENTRY_SIZE);
>      memset(dev->msix_pba, 0, QEMU_ALIGN_UP(dev->msix_entries_nr, 64) / 8);
> -    msix_mask_all(dev, dev->msix_entries_nr);
> +    msix_update_function_masked(dev);
>  }
>
>
> Then either no further changes to this patchset are necessary. Or, if
> relying on unmasks/masks (or
> msix_vector_use_notifier/msix_vector_release_notifier as it's called
> in msix.c) always being balanced is not recommended, the assert will
> simply change into an if.

This is fixed in "msix: don't mask already masked vectors on reset":
https://lists.gnu.org/archive/html/qemu-devel/2017-12/msg01362.html