Re: [Xen-devel] [PATCH v2] xen/pt: Fix a xen passthrough failure

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

Hello,

Thanks for the patch.

The subject should be more descriptive, "Fix a xen passthrough
failure" is too generic. How about: "allow passthrough of devices with
bogus interrupt pin" or something similar.

On Mon, Dec 03, 2018 at 12:04:38AM -0500, Zhao Yan wrote:
> For some pci device, even its PCI_INTERRUPT_PIN is not 0, it actually
> doesn't support INTx mode, so its machine irq read from host sysfs is 0.
> In that case, report PCI_INTERRUPT_PIN as 0 to guest and let passthrough
> continue.
> 
> v2: fix some coding style issue

The changelog between versions should be below the '---'.

> 
> Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Cc: Jan Beulich <JBeulich@xxxxxxxx>
> Signed-off-by: Zhao Yan <yan.y.zhao@xxxxxxxxx>
> ---
>  hw/xen/xen_pt.c             | 5 +++++
>  hw/xen/xen_pt_config_init.c | 8 +++++++-
>  2 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
> index f1f3a3727c..d601c9979c 100644
> --- a/hw/xen/xen_pt.c
> +++ b/hw/xen/xen_pt.c
> @@ -847,6 +847,11 @@ static void xen_pt_realize(PCIDevice *d, Error **errp)
>      }
>  
>      machine_irq = s->real_device.irq;
> +    if (machine_irq == 0) {
> +        XEN_PT_LOG(d, "machine irq is 0\n");

I would maybe consider disabling INTX assertion here on the command
register.

> +        goto out;
> +    }
> +
>      rc = xc_physdev_map_pirq(xen_xc, xen_domid, machine_irq, &pirq);
>      if (rc < 0) {
>          error_setg_errno(errp, errno, "Mapping machine irq %u to"
> diff --git a/hw/xen/xen_pt_config_init.c b/hw/xen/xen_pt_config_init.c
> index 47f9010c75..1007b6c977 100644
> --- a/hw/xen/xen_pt_config_init.c
> +++ b/hw/xen/xen_pt_config_init.c
> @@ -300,7 +300,13 @@ static int xen_pt_irqpin_reg_init(XenPCIPassthroughState 
> *s,
>                                    XenPTRegInfo *reg, uint32_t real_offset,
>                                    uint32_t *data)
>  {
> -    *data = xen_pt_pci_read_intx(s);
> +    if (s->real_device.irq)
> +        *data = xen_pt_pci_read_intx(s);
> +    else {
> +        XEN_PT_LOG(&s->dev,
> +            "machine irq is 0, init guest PCI_INTERRUPT_PIN to 0\n");
> +        *data = 0;

The default value for the register is already zero, so you could drop
the else branch AFAICT.

Thanks, Roger.

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