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

[Stefano Stabellini]

On Thu, 20 Feb 2014, Olaf Hering wrote:
> 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.

It needs to build at least.