Re: [RFC QEMU PATCH v4 1/1] xen: Use gsi instead of irq for mapping pirq

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 5 Jan 2024, Jiqian Chen wrote:
> In PVH dom0, it uses the linux local interrupt mechanism,
> when it allocs irq for a gsi, it is dynamic, and follow
> the principle of applying first, distributing first. And
> the irq number is alloced from small to large, but the
> applying gsi number is not, may gsi 38 comes before gsi
> 28, that causes the irq number is not equal with the gsi
> number. And when passthrough a device, qemu wants to use
> gsi to map pirq, xen_pt_realize->xc_physdev_map_pirq, but
> the gsi number is got from file
> /sys/bus/pci/devices/<sbdf>/irq in current code, so it
> will fail when mapping.
> 
> Add gsi into XenHostPCIDevice and use gsi number that
> read from gsi sysfs if it exists.
> 
> Co-developed-by: Huang Rui <ray.huang@xxxxxxx>
> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>  hw/xen/xen-host-pci-device.c | 7 +++++++
>  hw/xen/xen-host-pci-device.h | 1 +
>  hw/xen/xen_pt.c              | 6 +++++-
>  3 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/xen/xen-host-pci-device.c b/hw/xen/xen-host-pci-device.c
> index 8c6e9a1716a2..5be3279aa25b 100644
> --- a/hw/xen/xen-host-pci-device.c
> +++ b/hw/xen/xen-host-pci-device.c
> @@ -370,6 +370,13 @@ void xen_host_pci_device_get(XenHostPCIDevice *d, 
> uint16_t domain,
>      }
>      d->irq = v;
>  
> +    xen_host_pci_get_dec_value(d, "gsi", &v, errp);
> +    if (*errp) {
> +        d->gsi = -1;
> +    } else {
> +        d->gsi = v;
> +    }
> +
>      xen_host_pci_get_hex_value(d, "class", &v, errp);
>      if (*errp) {
>          goto error;
> diff --git a/hw/xen/xen-host-pci-device.h b/hw/xen/xen-host-pci-device.h
> index 4d8d34ecb024..74c552bb5548 100644
> --- a/hw/xen/xen-host-pci-device.h
> +++ b/hw/xen/xen-host-pci-device.h
> @@ -27,6 +27,7 @@ typedef struct XenHostPCIDevice {
>      uint16_t device_id;
>      uint32_t class_code;
>      int irq;
> +    int gsi;
>  
>      XenHostPCIIORegion io_regions[PCI_NUM_REGIONS - 1];
>      XenHostPCIIORegion rom;
> diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
> index 36e6f93c372f..d448f3a17306 100644
> --- a/hw/xen/xen_pt.c
> +++ b/hw/xen/xen_pt.c
> @@ -839,7 +839,11 @@ static void xen_pt_realize(PCIDevice *d, Error **errp)
>          goto out;
>      }
>  
> -    machine_irq = s->real_device.irq;
> +    if (s->real_device.gsi < 0) {
> +        machine_irq = s->real_device.irq;
> +    } else {
> +        machine_irq = s->real_device.gsi;
> +    }
>      if (machine_irq == 0) {
>          XEN_PT_LOG(d, "machine irq is 0\n");
>          cmd |= PCI_COMMAND_INTX_DISABLE;
> -- 
> 2.34.1
>