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From: | Jason J. Herne |
Subject: | Re: [Qemu-devel] [RFC 15/15] s390-bios: Use sense ccw to ensure consistent device state at boot time |
Date: | Fri, 6 Jul 2018 10:45:03 -0400 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 |
On 07/06/2018 06:08 AM, Cornelia Huck wrote:
On Thu, 5 Jul 2018 13:25:43 -0400 "Jason J. Herne" <address@hidden> wrote:If a vfio-ccw device is left in an error state (example: pending unit check) then it is possible for that state to persist for a vfio-ccw device even after the enable subchannel that we do to bring the device online. If this state is allowed to persist then even simple I/O operations will needlessly fail. A basic sense ccw is used to clear this error state for the boot device.Another thing: What about unsolicited interrupts? I.e., you enable the subchannel, and then it becomes pending with unsolicited status. Do you have any handling for that (or plan to add it)? We could ignore that for virtio devices, but probably not for dasds.
...
Hmm. Could an error condition reassert itself after it was cleared? Probably not worth spending too much time on, though.+ switch (cu_type(blk_schid)) { case 0x3990: /* Real DASD device */ dasd_ipl(blk_schid); /* no return */
I believe both of these issues to be the same as we are currently discussion in our replies to patch #10. My opinion posted there applies to this scenario. If my information is incorrect or you disagree with my assessment please yell at me! :-D
-- -- Jason J. Herne (address@hidden)
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