On Sat, 20 Jul 2024 at 23:11, Mostafa Saleh <smost...@google.com> wrote: > > Hi Peter, > > On Fri, Jul 19, 2024 at 04:57:18PM +0100, Peter Maydell wrote: > > On Fri, 19 Jul 2024 at 16:36, Julien Grall <jul...@xen.org> wrote: > > > > > > Hi, > > > > > > On 18/07/2024 10:43, Julien Grall wrote: > > > > Hi Eric, > > > > > > > > On 17/07/2024 18:43, Eric Auger wrote: > > > >> Hi Peter, Richard, > > > >> > > > >> On 7/17/24 17:09, Jean-Philippe Brucker wrote: > > > >>> On Mon, Jul 15, 2024 at 08:45:00AM +0000, Mostafa Saleh wrote: > > > >>>> Currently, QEMU supports emulating either stage-1 or stage-2 SMMUs > > > >>>> but not nested instances. > > > >>>> This patch series adds support for nested translation in SMMUv3, > > > >>>> this is controlled by property “arm-smmuv3.stage=nested”, and > > > >>>> advertised to guests as (IDR0.S1P == 1 && IDR0.S2P == 2) > > > >>> For the whole series (3-9, 11, 12, 15, 16, 18): > > > >>> > > > >>> Reviewed-by: Jean-Philippe Brucker <jean-phili...@linaro.org> > > > >>> > > > >>> (and I think patch 16 is missing Eric's R-b) > > > >> > > > >> Jean-Philippe and I have followed up the progress of this series, > > > >> Mostafa took into account all our comments and all the patches were > > > >> reviewed. It seems to be in a pretty decent state so if you don't have > > > >> any objection, please consider pulling it for 9.1. > > > >> > > > >> On my end I did some testing in non nesting mode with virtio-net/vhost > > > >> and I have not noticed any regression. > > > >> Would be nice if someone could send his T-b for the nested part though > > > >> (Julien?). > > > > > > > > I haven't yet tried the latest version. I will do that in the next > > > > couple of days. > > > I see this is already merged. If this still matters: > > > > > > Tested-by: Julien Grall <jgr...@amazon.com> > > > > We can't retrospectively add the tag, but the testing itself > > is still important -- thanks for doing it. > > > > Q: is there any reason not to: > > (a) change the default to "nested" rather than "1" > > (b) make the virt board (for new virt machine versions) use > > "nested"? > > > > AIUI "nested" should be a superset of "stage-1 only", the guest > > can just ignore stage-2 if it doesn't care about it. Or is > > there a performance hit from having stage-2 around even if the > > guest doesn't enable it? > > I didn’t do benchmarks, but from the code, I don’t think there > would be a difference from using stage-1 only or nested stages > with stage-1 config. > I didn’t make “nested” the default stage or used it for the virt > board, as I was worried about compatibility issues (I think that > breaks backward migration), but otherwise I don’t see issues. > > But if I understand correctly, setting that for virt board 9.1 > (virt_machine_9_1_options) would be fine?
Yes, we would need to retain the old stage-1-only config on the older machine version types, but we could switch to nested by default on the newer ones. It's a little late I think to make that change for the virt board at this point in the 9.1 release cycle, but we could do it for 9.2. thanks -- PMM
