Re: [QEMU PATCH v9] xen/passthrough: use gsi to map pirq when dom0 is PVH

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

On 10/24/24 05:06, Jiqian Chen wrote:
> diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
> index 3635d1b39f79..5b10d501d566 100644
> --- a/hw/xen/xen_pt.c
> +++ b/hw/xen/xen_pt.c
> @@ -766,6 +766,50 @@ static void xen_pt_destroy(PCIDevice *d) {
>  }
>  /* init */
>  
> +#if CONFIG_XEN_CTRL_INTERFACE_VERSION >= 42000
> +static bool xen_pt_need_gsi(void)
> +{
> +    FILE *fp;
> +    int len;
> +    char type[10];

A brief in-code comment to explain how you arrived at 10 would be
appreciated.

> +    const char *guest_type = "/sys/hypervisor/guest_type";
> +
> +    fp = fopen(guest_type, "r");
> +    if (fp == NULL) {
> +        error_report("Cannot open %s: %s", guest_type, strerror(errno));
> +        return false;
> +    }
> +    fgets(type, sizeof(type), fp);

Please check the return value of fgets.

> +    fclose(fp);
> +
> +    len = strlen(type);

Before passing to strlen, is "type" always guaranteed to have a
terminating '\0' character?

> +    if (len) {
> +        type[len - 1] = '\0';
> +        if (!strcmp(type, "PVH")) {
> +            return true;
> +        }
> +    }
> +    return false;
> +}
> +
> +static int xen_pt_map_pirq_for_gsi(PCIDevice *d, int *pirq)
> +{
> +    int gsi;
> +    XenPCIPassthroughState *s = XEN_PT_DEVICE(d);
> +
> +    gsi = xc_pcidev_get_gsi(xen_xc,
> +                            PCI_SBDF(s->real_device.domain,
> +                                     s->real_device.bus,
> +                                     s->real_device.dev,
> +                                     s->real_device.func));
> +    if (gsi >= 0) {
> +        return xc_physdev_map_pirq_gsi(xen_xc, xen_domid, gsi, pirq);
> +    }
> +
> +    return gsi;
> +}
> +#endif
> +
>  static void xen_pt_realize(PCIDevice *d, Error **errp)
>  {
>      ERRP_GUARD();
> @@ -847,7 +891,16 @@ static void xen_pt_realize(PCIDevice *d, Error **errp)
>          goto out;
>      }
>  
> +#if CONFIG_XEN_CTRL_INTERFACE_VERSION >= 42000
> +    if (xen_pt_need_gsi()) {
> +        rc = xen_pt_map_pirq_for_gsi(d, &pirq);
> +    } else {
> +        rc = xc_physdev_map_pirq(xen_xc, xen_domid, machine_irq, &pirq);
> +    }
> +#else
>      rc = xc_physdev_map_pirq(xen_xc, xen_domid, machine_irq, &pirq);
> +#endif
> +
>      if (rc < 0) {
>          XEN_PT_ERR(d, "Mapping machine irq %u to pirq %i failed, (err: 
> %d)\n",
>                     machine_irq, pirq, errno);
> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> index eb26cac81098..07805aa8a5f3 100644
> --- a/include/hw/pci/pci.h
> +++ b/include/hw/pci/pci.h
> @@ -23,6 +23,10 @@ extern bool pci_available;
>  #define PCI_SLOT_MAX            32
>  #define PCI_FUNC_MAX            8
>  
> +#define PCI_SBDF(seg, bus, dev, func) \
> +            ((((uint32_t)(seg)) << 16) | \
> +            (PCI_BUILD_BDF(bus, PCI_DEVFN(dev, func))))
> +
>  /* Class, Vendor and Device IDs from Linux's pci_ids.h */
>  #include "hw/pci/pci_ids.h"
>