Re: [Qemu-devel] [PATCH for v1.0 1/3] msix: track function masked in pci device state

[Cam Macdonell]

On Mon, Dec 5, 2011 at 2:08 AM, Michael S. Tsirkin <address@hidden> wrote:
> On Sun, Dec 04, 2011 at 04:47:17PM -0700, Cam Macdonell wrote:
>> On Sun, Dec 4, 2011 at 3:20 AM, Michael S. Tsirkin <address@hidden> wrote:
>> > On Fri, Dec 02, 2011 at 04:34:21PM -0700, Cam Macdonell wrote:
>> >> Based on a git bisect, this patch breaks msi-x interrupt delivery in
>> >> the ivshmem device.
>> >
>> > I think the following should fix it. Compiled-only -
>> > could you pls check? If yes let's apply to the stable branch.
>>
>> Thanks for the patch Michael.
>>
>> It addresses the need for msix_write_config() to be called, but the
>> addition of the msix_reset() is causing a reset of the vectors after
>> they've been initialized in pci_ivshmem_init().  So, interrupts still
>> aren't delivered with this patch applied as it is.
>>
>> In particular, a reset occurs after pci_ivshmem_init runs, so the
>> msix_entry_used array is reset to 0s, which causes the interrupt
>> delivery to fail.
>>
>> If I comment out the msix_reset(), then interrupts are delivered.
>> Would the reset be caused by a bug in the guest driver?  or do I need
>> to reconfigure the msix after reset?  I'm unclear as to the proper
>> behaviour after a reset.
>>
>> Thanks,
>> Cam
>>
>
> I didn't anticipate this, virtio only configures vectors when msi-x is 
> enabled.
> For 1.0 it's safest to do the same and just re-enable after reset.
>
> So we'll end up with something like the following - does it help?

Yes, this fixes interrupt delivery.

>
> Side note: exit(1) is not the best way to handle
> errors in the init function. I think you should add error_report, then
> goto err on failures to init, cleanup what you have set up
> meanwhile and return an error code.

Thanks, I'll fix that.

>
> diff --git a/hw/ivshmem.c b/hw/ivshmem.c
> index 242fbea..c58f4d3 100644
> --- a/hw/ivshmem.c
> +++ b/hw/ivshmem.c
> @@ -500,11 +500,29 @@ static void ivshmem_read(void *opaque, const uint8_t * 
> buf, int flags)
>     return;
>  }
>
> +/* Select the MSI-X vectors used by device.
> + * ivshmem maps events to vectors statically, so
> + * we just enable all vectors on init and after reset. */
> +static void ivshmem_use_msix(IVShmemState * s)
> +{
> +    int i;
> +
> +    if (!msix_present(&s->dev)) {
> +        return;
> +    }
> +
> +    for (i = 0; i < s->vectors; i++) {
> +        msix_vector_use(&s->dev, i);
> +    }
> +}
> +
>  static void ivshmem_reset(DeviceState *d)
>  {
>     IVShmemState *s = DO_UPCAST(IVShmemState, dev.qdev, d);
>
>     s->intrstatus = 0;
> +    msix_reset(&s->dev);
> +    ivshmem_use_msix(s);
>     return;
>  }
>
> @@ -535,12 +553,8 @@ static uint64_t ivshmem_get_size(IVShmemState * s) {
>     return value;
>  }
>
> -static void ivshmem_setup_msi(IVShmemState * s) {
> -
> -    int i;
> -
> -    /* allocate the MSI-X vectors */
> -
> +static void ivshmem_setup_msi(IVShmemState * s)
> +{
>     memory_region_init(&s->msix_bar, "ivshmem-msix", 4096);
>     if (!msix_init(&s->dev, s->vectors, &s->msix_bar, 1, 0)) {
>         pci_register_bar(&s->dev, 1, PCI_BASE_ADDRESS_SPACE_MEMORY,
> @@ -551,13 +565,10 @@ static void ivshmem_setup_msi(IVShmemState * s) {
>         exit(1);
>     }
>
> -    /* 'activate' the vectors */
> -    for (i = 0; i < s->vectors; i++) {
> -        msix_vector_use(&s->dev, i);
> -    }
> -
>     /* allocate Qemu char devices for receiving interrupts */
>     s->eventfd_table = g_malloc0(s->vectors * sizeof(EventfdEntry));
> +
> +    ivshmem_use_msix(s);
>  }
>
>  static void ivshmem_save(QEMUFile* f, void *opaque)
> @@ -610,6 +621,13 @@ static int ivshmem_load(QEMUFile* f, void *opaque, int 
> version_id)
>     return 0;
>  }
>
> +static void ivshmem_write_config(PCIDevice *pci_dev, uint32_t address,
> +                                uint32_t val, int len)
> +{
> +    pci_default_write_config(pci_dev, address, val, len);
> +    msix_write_config(pci_dev, address, val, len);
> +}
> +
>  static int pci_ivshmem_init(PCIDevice *dev)
>  {
>     IVShmemState *s = DO_UPCAST(IVShmemState, dev, dev);
> @@ -734,6 +752,8 @@ static int pci_ivshmem_init(PCIDevice *dev)
>
>     }
>
> +    s->dev.config_write = ivshmem_write_config;
> +
>     return 0;
>  }
>
>