Re: [Xen-devel] [PATCH v2 2/4] libxl: attach PCI device to qemu only after setting pciback/pcifront

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

On Tue, Jan 15, 2019 at 04:36:29PM +0100, Marek Marczykowski-Górecki wrote:
> When qemu is running in stubdomain, handling "pci-ins" command will fail
> if pcifront is not initialized already. Fix this by sending such command
> only after confirming that pciback/front is running.
> 
> Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> ---
> Changes in v2:
> - Fixed code style since previous version.
> ---
>  tools/libxl/libxl_pci.c |  9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/tools/libxl/libxl_pci.c b/tools/libxl/libxl_pci.c
> index 3b6b23c..1bde537 100644
> --- a/tools/libxl/libxl_pci.c
> +++ b/tools/libxl/libxl_pci.c
> @@ -1191,6 +1191,7 @@ int libxl__device_pci_add(libxl__gc *gc, uint32_t 
> domid, libxl_device_pci *pcide
>  {
>      libxl_ctx *ctx = libxl__gc_owner(gc);
>      unsigned int orig_vdev, pfunc_mask;
> +    char *be_path;
>      libxl_device_pci *assigned;
>      int num_assigned, i, rc;
>      int stubdomid = 0;
> @@ -1245,6 +1246,14 @@ int libxl__device_pci_add(libxl__gc *gc, uint32_t 
> domid, libxl_device_pci *pcide
>          rc = do_pci_add(gc, stubdomid, &pcidev_s, 0);
>          if ( rc )
>              goto out;
> +        /* Wait for the device actually being connected, otherwise device 
> model
> +         * running there will fail to find the device. */
> +        be_path = libxl__sprintf(gc, "%s/backend/pci/%d/0",
> +                                 libxl__xs_get_dompath(gc, 0), stubdomid);
> +        rc = libxl__wait_for_backend(gc, be_path,
> +                                     GCSPRINTF("%d", XenbusStateConnected));
> +        if (rc)
> +            goto out;

I think it would be better to use the async libxl functionality here,
see libxl__xswait_start. I will leave for the toolstack maintainers to
decide. Apart from that the change seems correct.

Thanks, Roger.

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