Re: [Qemu-devel] [PATCH v3 12/16] s390-bios: Refactor virtio to run channel programs via cio

[Cornelia Huck <cohuck@redhat.com>]

On Thu, 7 Mar 2019 10:09:46 -0500
"Jason J. Herne" <jjherne@linux.ibm.com> wrote:

> On 3/5/19 7:30 AM, Cornelia Huck wrote:
> > On Fri,  1 Mar 2019 13:59:32 -0500
> > "Jason J. Herne" <jjherne@linux.ibm.com> wrote:
> >   
> >> Now that we have a Channel I/O library let's modify virtio boot code to
> >> make use of it for running channel programs.
> >>
> >> Signed-off-by: Jason J. Herne <jjherne@linux.ibm.com>
> >> ---
> >>   pc-bios/s390-ccw/virtio.c | 49 +++++++++++++++++++----------------------------
> >>   1 file changed, 20 insertions(+), 29 deletions(-)
> >>
> >> diff --git a/pc-bios/s390-ccw/virtio.c b/pc-bios/s390-ccw/virtio.c
> >> index aa9da72..711daf5 100644
> >> --- a/pc-bios/s390-ccw/virtio.c
> >> +++ b/pc-bios/s390-ccw/virtio.c
> >> @@ -14,6 +14,7 @@
> >>   #include "virtio.h"
> >>   #include "virtio-scsi.h"
> >>   #include "bswap.h"
> >> +#include "helper.h"
> >>   
> >>   #define VRING_WAIT_REPLY_TIMEOUT 30
> >>   
> >> @@ -89,33 +90,20 @@ int drain_irqs(SubChannelId schid)
> >>       }
> >>   }
> >>   
> >> -static int run_ccw(VDev *vdev, int cmd, void *ptr, int len)
> >> +static int run_ccw(VDev *vdev, int cmd, void *ptr, int len, bool sli)
> >>   {
> >>       Ccw1 ccw = {};
> >> -    CmdOrb orb = {};
> >> -    int r;
> >> -
> >> -    enable_subchannel(vdev->schid);
> >> -
> >> -    /* start subchannel command */
> >> -    orb.fmt = 1;
> >> -    orb.cpa = (u32)(long)&ccw;
> >> -    orb.lpm = 0x80;
> >>   
> >>       ccw.cmd_code = cmd;
> >>       ccw.cda = (long)ptr;
> >>       ccw.count = len;
> >>   
> >> -    r = ssch(vdev->schid, &orb);
> >> -    /*
> >> -     * XXX Wait until device is done processing the CCW. For now we can
> >> -     *     assume that a simple tsch will have finished the CCW processing,
> >> -     *     but the architecture allows for asynchronous operation
> >> -     */
> >> -    if (!r) {
> >> -        r = drain_irqs(vdev->schid);
> >> +    if (sli) {
> >> +        ccw.flags |= CCW_FLAG_SLI;
> >>       }
> >> -    return r;
> >> +
> >> +    enable_subchannel(vdev->schid);  
> > 
> > As said, maybe just move this to the main routine, instead of having to
> > call this here again and again.
> >   
> 
> I can just remove this call all together, but because of the netboot case I'll need to add 
> a call to enable_subchannel to virtio_is_supported() or find_net_dev().
> 
> netmain.c: main -> virtio_setup-> find_net_dev-> virtio_is_supported
> 
> Let me know if you like this idea or not. If you're okay with it, I'll queue it up for v4. 
> IMHO, adding the call to find_net_dev makes more sense than virtio_is_supported.

I think adding the call to find_net_dev() would make sense.

> 
> 
> >> +    return do_cio(vdev->schid, ptr2u32(&ccw), CCW_FMT1);
> >>   }
> >>   
> >>   static void vring_init(VRing *vr, VqInfo *info)  
> > 
> > (...)
> >   
> >> @@ -324,7 +314,8 @@ bool virtio_is_supported(SubChannelId schid)
> >>       vdev.schid = schid;
> >>       memset(&vdev.senseid, 0, sizeof(vdev.senseid));
> >>       /* run sense id command */
> >> -    if (run_ccw(&vdev, CCW_CMD_SENSE_ID, &vdev.senseid, sizeof(vdev.senseid))) {
> >> +    if (run_ccw(&vdev, CCW_CMD_SENSE_ID, &vdev.senseid, sizeof(vdev.senseid),
> >> +                true)) {
> >>           return false;
> >>       }
> >>       if (vdev.senseid.cu_type == 0x3832) {  
> > 
> > Can't you use the new routine for obtaining the cu type here?
> >   
> 
> cu_type only returns the control unit type. This code goes on to look at the model number 
> as well. In hind sight, I could have noticed this and simply structured my code to return 
> the whole sense_id data structure. I'm not against making this change, but things seem 
> pretty clean as they are. :)

I find having two different places that do SENSE_ID a bit odd :)

But no really strong opinion here; I'll happily leave the decision to
the boot code maintainers.