lkml.org 
[lkml]   [2018]   [May]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 04/10] vfio: ccw: replace IO_REQ event with SSCH_REQ event
From
Date
On 30/04/2018 17:30, Cornelia Huck wrote:
> On Wed, 25 Apr 2018 15:52:19 +0200
> Pierre Morel <pmorel@linux.vnet.ibm.com> wrote:
>
>> On 25/04/2018 10:41, Cornelia Huck wrote:
>>> On Thu, 19 Apr 2018 16:48:07 +0200
>>> Pierre Morel<pmorel@linux.vnet.ibm.com> wrote:
>>>> diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
>>>> index 3284e64..93aab87 100644
>>>> --- a/drivers/s390/cio/vfio_ccw_private.h
>>>> +++ b/drivers/s390/cio/vfio_ccw_private.h
>>>> @@ -76,7 +76,7 @@ enum vfio_ccw_state {
>>>> */
>>>> enum vfio_ccw_event {
>>>> VFIO_CCW_EVENT_NOT_OPER,
>>>> - VFIO_CCW_EVENT_IO_REQ,
>>>> + VFIO_CCW_EVENT_SSCH_REQ,
>>>> VFIO_CCW_EVENT_INTERRUPT,
>>>> VFIO_CCW_EVENT_SCH_EVENT,
>>>> /* last element! */
>>> I don't think we should separate the ssch handling. The major
>>> difference to halt/clear is that it needs channel program translation.
>>> Everything else (issuing the instruction and processing the interrupt)
>>> are basically the same. If we just throw everything at the hardware
>>> and let the host's channel subsystem figure it out, we already should
>>> be fine with regard to most of the races.
>> We must test at a moment or another the kind of request we do,
>> cancel, halt and clear only need the subchannel id in register 1 and as
>> you said are much more direct to implement.
>>
>> If we do not separate them here, we need a switch in the "do_io_request"
>> function.
>> Is it what you mean?
> Yes. Most of the handling should be the same for any function.

I really don't know, the 4 functions are quite different.

- SSCH uses an ORB, and has a quite long kernel execution time for VFIO
- there is a race between SSCH and the others instructions
- XSCH makes subchannel no longer start pending, also reset the busy
indications
- CSCH cancels both SSCH and HSCH instruction, and perform path management
- HSCH has different busy (entry) conditions

But since they are not implemented today, I can keep the old name.



--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany

\
 
 \ /
  Last update: 2018-05-03 14:07    [W:0.114 / U:1.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site