Re: [Qemu-devel] [PATCH v2] xen_disk: add discard support

[Olaf Hering <olaf@aepfle.de>]

On Thu, Feb 20, Stefano Stabellini wrote:

> On Thu, 6 Feb 2014, Olaf Hering wrote:
> > @@ -253,6 +254,8 @@ static int ioreq_parse(struct ioreq *ioreq)
> >      case BLKIF_OP_WRITE:
> >          ioreq->prot = PROT_READ; /* from memory */
> >          break;
> > +    case BLKIF_OP_DISCARD:
> > +        return 0;
> >      default:
> >          xen_be_printf(&blkdev->xendev, 0, "error: unknown operation (%d)\n",
> >                        ioreq->req.operation);
> 
> Unfortunately I didn't realize before that older Xen releases don't
> define BLKIF_OP_DISCARD, therefore this patch would cause QEMU build
> failures against Xen 4.1 for example.

Why would that matter?
Is new qemu seriously supposed to work with stale Xen releases?
But I will have a look how to solve this.

Olaf