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  1. Bug #1495983
  2. Comment #24

Comment 24 for bug 1495983

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Joseph Salisbury (jsalisbury) wrote : Re: [Hyper-V] kernel panic occurs when installing Ubuntu Server 15.10 x32

Thanks for the update, Chris. The patch "storvsc: use small sg_tablesize on x86" has not landed in mainline yet, but I can submit an SRU request to include it as an Ubuntu SAUCE patch.

However, for Trusty I think we need to increase MAX_PAGE_BUFFER_COUNT in addition to the patch "storvsc: use small sg_tablesize on x86". In my testing a Trusty kernel with only the storvsc patch will still panic. But a Trusty kernel with the storvsc patch and a value of 32 for MAX_PAGE_BUFFER_COUNT will not panic.

There was actually a commit in v3.15-rc1, written by KY:
commit 7e5ec36834a5752304dc0751dfab42ba6ad64a85
Author: K. Y. Srinivasan <email address hidden>
Date: Fri Mar 7 00:10:34 2014 -0800

    Drivers: hv: vmbus: Increase the limit on the number of pfns we can handle

So for Trusty I think we need commit 7e5ec368 and the patch "storvsc: use small sg_tablesize on x86".

I built two Trusty test kernels. One has only the "storvsc: use small sg_tablesize on x86" patch. The other has a cherry pick of commit 7e5ec368 and the "storvsc: use small sg_tablesize on x86" patch.

Ovidiu R, if you have a chance can you test these two kernels? Before I submit the new patch, I'd like to confirm if we also need commit 7e5ec368 or not.

Test kernel with only the new patch:
http://kernel.ubuntu.com/~jsalisbury/lp1495983/patched-kernel/trusty/trusty-with-only-use-small-sg_tablesize/

Test kernel with the new patch and a cherry pick of 7e5ec368:
http://kernel.ubuntu.com/~jsalisbury/lp1495983/patched-kernel/trusty/trusty-with-use-small-sg_tablesizeANDCommit7e5ec368/