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

["Jason J. Herne" <jjherne@linux.ibm.com>]

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.


>> +    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. :)

-- 
-- Jason J. Herne (jjherne@linux.ibm.com)