Christian Borntraeger
2019-Dec-18 15:59 UTC
vhost changes (batched) in linux-next after 12/13 trigger random crashes in KVM guests after reboot
On 18.12.19 16:10, Michael S. Tsirkin wrote:> On Wed, Dec 18, 2019 at 03:43:43PM +0100, Christian Borntraeger wrote: >> Michael, >> >> with >> commit db7286b100b503ef80612884453bed53d74c9a16 (refs/bisect/skip-db7286b100b503ef80612884453bed53d74c9a16) >> vhost: use batched version by default >> plus >> commit 6bd262d5eafcdf8cdfae491e2e748e4e434dcda6 (HEAD, refs/bisect/bad) >> Revert "vhost/net: add an option to test new code" >> to make things compile (your next tree is not easily bisectable, can you fix that as well?). > > I'll try. > >> >> I get random crashes in my s390 KVM guests after reboot. >> Reverting both patches together with commit decd9b8 "vhost: use vhost_desc instead of vhost_log" to >> make it compile again) on top of linux-next-1218 makes the problem go away. >> >> Looks like the batched version is not yet ready for prime time. Can you drop these patches until >> we have fixed the issues? >> >> Christian >> > > Will do, thanks for letting me know.I have confirmed with the initial reporter (internal test team) that <driver name='qemu'/> with a known to be broken linux next kernel also fixes the problem, so it is really the vhost changes.
Michael S. Tsirkin
2020-Jan-06 10:50 UTC
vhost changes (batched) in linux-next after 12/13 trigger random crashes in KVM guests after reboot
On Wed, Dec 18, 2019 at 04:59:02PM +0100, Christian Borntraeger wrote:> On 18.12.19 16:10, Michael S. Tsirkin wrote: > > On Wed, Dec 18, 2019 at 03:43:43PM +0100, Christian Borntraeger wrote: > >> Michael, > >> > >> with > >> commit db7286b100b503ef80612884453bed53d74c9a16 (refs/bisect/skip-db7286b100b503ef80612884453bed53d74c9a16) > >> vhost: use batched version by default > >> plus > >> commit 6bd262d5eafcdf8cdfae491e2e748e4e434dcda6 (HEAD, refs/bisect/bad) > >> Revert "vhost/net: add an option to test new code" > >> to make things compile (your next tree is not easily bisectable, can you fix that as well?). > > > > I'll try. > > > >> > >> I get random crashes in my s390 KVM guests after reboot. > >> Reverting both patches together with commit decd9b8 "vhost: use vhost_desc instead of vhost_log" to > >> make it compile again) on top of linux-next-1218 makes the problem go away. > >> > >> Looks like the batched version is not yet ready for prime time. Can you drop these patches until > >> we have fixed the issues? > >> > >> Christian > >> > > > > Will do, thanks for letting me know. > > I have confirmed with the initial reporter (internal test team) that <driver name='qemu'/> > with a known to be broken linux next kernel also fixes the problem, so it is really the > vhost changes.OK I'm back and trying to make it more bisectable. I pushed a new tag "batch-v2". It's same code but with this bisect should get more information. I suspect one of the following: commit 1414d7ee3d10d2ec2bc4ee652d1d90ec91da1c79 Author: Michael S. Tsirkin <mst at redhat.com> Date: Mon Oct 7 06:11:18 2019 -0400 vhost: batching fetches With this patch applied, new and old code perform identically. Lots of extra optimizations are now possible, e.g. we can fetch multiple heads with copy_from/to_user now. We can get rid of maintaining the log array. Etc etc. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> commit 50297a8480b439efc5f3f23088cb2d90b799acef Author: Michael S. Tsirkin <mst at redhat.com> Date: Wed Dec 11 12:19:26 2019 -0500 vhost: use batched version by default As testing shows no performance change, switch to that now. Signed-off-by: Michael S. Tsirkin <mst at redhat.com> and would like to know which. Thanks!
Christian Borntraeger
2020-Jan-07 08:59 UTC
vhost changes (batched) in linux-next after 12/13 trigger random crashes in KVM guests after reboot
On 06.01.20 11:50, Michael S. Tsirkin wrote:> On Wed, Dec 18, 2019 at 04:59:02PM +0100, Christian Borntraeger wrote: >> On 18.12.19 16:10, Michael S. Tsirkin wrote: >>> On Wed, Dec 18, 2019 at 03:43:43PM +0100, Christian Borntraeger wrote: >>>> Michael, >>>> >>>> with >>>> commit db7286b100b503ef80612884453bed53d74c9a16 (refs/bisect/skip-db7286b100b503ef80612884453bed53d74c9a16) >>>> vhost: use batched version by default >>>> plus >>>> commit 6bd262d5eafcdf8cdfae491e2e748e4e434dcda6 (HEAD, refs/bisect/bad) >>>> Revert "vhost/net: add an option to test new code" >>>> to make things compile (your next tree is not easily bisectable, can you fix that as well?). >>> >>> I'll try. >>> >>>> >>>> I get random crashes in my s390 KVM guests after reboot. >>>> Reverting both patches together with commit decd9b8 "vhost: use vhost_desc instead of vhost_log" to >>>> make it compile again) on top of linux-next-1218 makes the problem go away. >>>> >>>> Looks like the batched version is not yet ready for prime time. Can you drop these patches until >>>> we have fixed the issues? >>>> >>>> Christian >>>> >>> >>> Will do, thanks for letting me know. >> >> I have confirmed with the initial reporter (internal test team) that <driver name='qemu'/> >> with a known to be broken linux next kernel also fixes the problem, so it is really the >> vhost changes. > > OK I'm back and trying to make it more bisectable. > > I pushed a new tag "batch-v2". > It's same code but with this bisect should get more information.I get the following with this tag drivers/vhost/net.c: In function ?vhost_net_tx_get_vq_desc?: drivers/vhost/net.c:574:7: error: implicit declaration of function ?vhost_get_vq_desc_batch?; did you mean ?vhost_get_vq_desc?? [-Werror=implicit-function-declaration] 574 | r = vhost_get_vq_desc_batch(tvq, tvq->iov, ARRAY_SIZE(tvq->iov), | ^~~~~~~~~~~~~~~~~~~~~~~ | vhost_get_vq_desc
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