[libvirt PATCH 1/2] conf: add killpriv v2 attribute for virtiofs
Ján Tomko
jtomko at redhat.com
Thu Jan 6 15:27:01 UTC 2022
On a Wednesday in 2022, Daniel P. Berrangé wrote:
>On Wed, Jan 05, 2022 at 04:06:49PM +0100, Ján Tomko wrote:
>> Add a new attribute to control the killpriv feature:
>>
>> <filesystem>
>> ...
>> <binary>
>> <killpriv v2='off'/>
>> </binary>
>> </filesystem>
>
>Ewww, ewww, ewww.
>
>This is a horrible element & attribute name. Even with the docs I have
>little clue as to why we would ever need this or what its real effects
>are. Having now read the libvirt and related QEMU bugzilla, I now see
>that killpriv v2 is enabled by default in virtiofs because it is
>faster and more reliable. A limitation in NFS, however, means that
>some specific syscalls don't work correctly with it, so QEMU folks
>are saying killpriv v2 should not be used with NFS.
>
Thank you for the short summary of the bug, I did not realize it was
private :(
Jano
>At this point I ask why doesn't virtiofsd just do the right thing.
>It can statfs() the root of the export it is configured with and see
>that it is NFS. I'm not convinced by a need to expose this knob in
>libvirt, especially with such an unintelligible name & difficult to
>understand behavioural impact.
>
>>
>> https://bugzilla.redhat.com/show_bug.cgi?id=1972571
>>
>> Signed-off-by: Ján Tomko <jtomko at redhat.com>
>> ---
>> docs/formatdomain.rst | 4 ++++
>> docs/schemas/domaincommon.rng | 7 +++++++
>> src/conf/domain_conf.c | 15 +++++++++++++++
>> src/conf/domain_conf.h | 1 +
>> .../qemuxml2argvdata/vhost-user-fs-fd-memory.xml | 1 +
>> 5 files changed, 28 insertions(+)
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