[Bug] Crystal Ridge - Flush requests from Linux guests vs Host Filesystem fsync()

[Alice Liu]

Description:

In the filesystem-dax case guests flush requests to pmem must turn around and trigger fsync on the kvm-host / dom0 filesystem.

More background here:

https://lists.gnu.org/archive/html/qemu-devel/2017-04/msg03435.html

Target Qemu: 2.12
Target Release: 18.04

[Alice Liu (dxliu)]

Merged in Qemu 2.12.
Commit ids:
9837684316
cb836434cd
da6789c27c

[Seth Forshee (sforshee)]

I don't see any kernel fixes related to this request, so I'm thinking the kernel tag was added by mistake. Can you confirm?

[quanxian (quanxian-wang)]

This is qemu 2.12 instead of kernel

[Jeff Lane  (bladernr)]

Notified dpb to see if this fix can be picked up for Bionic.

[Christian Ehrhardt  (paelzer)]

da6789c27c is a no-op (functionally) but needed to make the patches apply as-is.

Rest is applying cleanly, with the exception of the documentation changes that miss some context (other options got documented more verbosely) - but that was easy to adapt.

In general it is adding new options and rather late to the cycle, but it is a bug (not able to handle dax correctly without) so it is more a fix than a feature.
All is default off/unused and it just is a fix that works through users (or tools) now being able to specify needs better.
=> No FFE needed, this really is more a fix (and being by default unused options should have rather low risk)

First shot at this is currently building in PPA [1]

I'll tonight make them part of a re-run of the regression tests for the coming upload (if build succeeds).

[1]: https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/3225/+packages

[Christian Ehrhardt  (paelzer)]

Also the changes are now public anyway - can we mark this non-private now?

[[e-mail] (pragyan)]

Yes this can be changed to public.

[Christian Ehrhardt  (paelzer)]

This bug was fixed in the package qemu - 1:2.11+dfsg-1ubuntu6

---------------
qemu (1:2.11+dfsg-1ubuntu6) bionic; urgency=medium

  * Remove LP: 1752026 changes to d/p/ubuntu/define-ubuntu-machine-types.patch.
    The Kernel fixes are preferred and already committed to the kernel.
    Therefore remove the default disabling of the HTM feature (LP: #1761175)
  * d/p/ubuntu/lp1739665-SSE-AVX-AVX512-cpu-features.patch: Enable new
    SSE/AVX/AVX512 cpu features (LP: #1739665)
  * d/p/ubuntu/lp1740219-continuous-space-commpage.patch: make Arm
    space+commpage continuous which avoids long startup times on
    qemu-user-static (LP: #1740219)
  * d/p/ubuntu/lp-1761372-*: provide pseries-bionic-2.11-sxxm type as
    convenience with all meltdown/spectre workarounds enabled by default.
    This is not the default type following upstream and x86 on that.
    (LP: #1761372).
  * d/p/ubuntu/lp-1704312-1-* provide means to manually handle filesystem-dax
    with pmem by backporting align and unarmed options (LP: #1704312).
  * d/p/ubuntu/lp-1762315-slirp-Add-domainname.patch: slirp: Add domainname
    option to slirp's DHCP server (LP: #1762315)

 -- Christian Ehrhardt <email address hidden> Wed, 04 Apr
2018 15:16:07 +0200