[PATCH 2/2] qemu: Generate command line for tb-cache feature

Michal Prívozník mprivozn at redhat.com
Fri Nov 5 08:28:56 UTC 2021


On 11/4/21 6:51 PM, Kashyap Chamarthy wrote:
> On Thu, Nov 04, 2021 at 01:22:53PM +0100, Michal Privoznik wrote:
>> Alright, here's the deal: to enable tb-cache one has to use
>> '-accel tcg,tb-size=' which then conflicts with '-machine
>> accel=tcg'. But sure, we can use the old -accel in this specific
>> case. But because of how the tb-size argument is defined in QEMU
>> there's no way for us to have a capability check. The feature was
>> introduced in QEMU commit of v5.0.0-rc0~175^2~62 and is tied to
>> TCG only. Therefore, I think we can live without capability
>> check. Worst case scenario, QEMU fails to start.
> 
> Hmm, you write: "... we can use the old -accel",  I was told by Paolo
> Bonzini the other day that "-accel" is preferred  instead of "-machine
> accel".   Hence I filed this GitLab ticket a couple of days:
> 
>     https://gitlab.com/libvirt/libvirt/-/issues/233 (Use `-accel`
>     instead of `-machine accel`)
> 
> [...]
> 

Yeah, I don't know why I thought that -accel was older than -machine
accel. Silly me :-) let me post v2.

Michal




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