On Tue, Jan 12, 2021 at 19:20:58 +0100, Igor Mammedov wrote:
On Tue, 12 Jan 2021 12:35:19 +0100 Peter Krempa <pkrempa@redhat.com> wrote:
On Tue, Jan 12, 2021 at 12:29:58 +0100, Michal Privoznik wrote:
On 1/12/21 12:19 PM, Peter Krempa wrote:
On Tue, Jan 12, 2021 at 09:29:49 +0100, Michal Privoznik wrote:
This capability tracks whether memory-backend-file has "x-use-canonical-path-for-ramblock-id" attribute. Introduced into QEMU by commit v4.0.0-rc0~189^2. While "x-" prefix is considered
Please use a commit hash instead of this.
experimental or internal to QEMU, the next commit justifies its use.
NACK unless qemu adds a statement to their code and documentation that the this property is considered stable despite the 'x-prefix' and you add a link to the appropriate qemu upstream commit once it's done.
We don't want to depend on experimental stuff so we need a strong excuse.
That's done in the next commit. Do you want me to copy it here too? I figured I'd put the justification where I'm actually setting the internal knob.
Yes, because this is also mentioning the an 'x-' prefixed property. I want to be absolutely clear in any places (including a comment in the code, which you also should add into the capability code) that this is extraordinary circumstance and that qemu is actually considering that property stable.
the only reason to keep x- prefix in this case is to cause less issues for downstream QEMUs. Since this compat property is copied to their own machine types. If we keep prefix downstream doesn't have to do anything, if we rename it, then downstreams have to carry a separate patch that does the same for their old machine types.
That would be okay if it's limited to past versions, but in this instance it is not. Allowing x-prefixed properties for any future release is a dangerous precedent. If we want to allow to detect the capability also for future release, we must declare that it's for a very particular reason and also that qemu will not delete it at will. This is to prevent any future discussions of unwaranted usage of x-prefixed properties in libvirt.