On Fri, Aug 14, 2020 at 02:54:38PM +0200, Jürgen Groß wrote: > On 14.08.20 14:47, Roger Pau Monné wrote: > > On Fri, Aug 14, 2020 at 12:27:32PM +0200, Jürgen Groß wrote: > > > On 14.08.20 11:56, Roger Pau Monné wrote: > > > > On Fri, Aug 14, 2020 at 08:29:20AM +0100, Christoph Hellwig wrote: > > > > > On Thu, Aug 13, 2020 at 09:54:20AM +0200, Roger Pau Monn?? wrote: > > > > > > On Thu, Aug 13, 2020 at 08:33:37AM +0100, Christoph Hellwig wrote: > > > > > > > On Tue, Aug 11, 2020 at 11:44:47AM +0200, Roger Pau Monne wrote: > > > > > > > > If enabled (because ZONE_DEVICE is supported) the usage of the new > > > > > > > > functionality untangles Xen balloon and RAM hotplug from the usage of > > > > > > > > unpopulated physical memory ranges to map foreign pages, which is the > > > > > > > > correct thing to do in order to avoid mappings of foreign pages depend > > > > > > > > on memory hotplug. > > > > > > > > > > > > > > So please just select ZONE_DEVICE if this is so much better rather > > > > > > > than maintaining two variants. > > > > > > > > > > > > We still need to other variant for Arm at least, so both need to be > > > > > > maintained anyway, even if we force ZONE_DEVICE on x86. > > > > > > > > > > Well, it still really helps reproducability if you stick to one > > > > > implementation of x86. > > > > > > > > > > The alternative would be an explicit config option to opt into it, > > > > > but just getting a different implementation based on a random > > > > > kernel option is strange. > > > > > > > > Would adding something like the chunk below to the patch be OK? > > > > > > > > ---8<--- > > > > diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig > > > > index 018020b91baa..5f321a1319e6 100644 > > > > --- a/drivers/xen/Kconfig > > > > +++ b/drivers/xen/Kconfig > > > > @@ -328,7 +328,14 @@ config XEN_FRONT_PGDIR_SHBUF > > > > tristate > > > > config XEN_UNPOPULATED_ALLOC > > > > - bool > > > > - default y if ZONE_DEVICE && !ARM && !ARM64 > > > > + bool "Use unpopulated memory ranges for guest mappings" > > > > + depends on X86 > > > > + select ZONE_DEVICE > > > > + default y > > > > > > I'd rather use "default XEN_BACKEND" here, as mappings of other guest's > > > memory is rarely used for non-backend guests. > > > > There's also the privcmd and gnt devices which make heavy use of this, > > so I'm not sure only selecting by default on XEN_BACKEND is the best > > option. > > I just want to avoid that kernels built for running as Xen guest, but > not as dom0, will be forced to select ZONE_DEVICE. > > As privcmd is dom0-only, this is no problem. Oh, didn't know that, I somehow assumed privcmd would be available to all Xen guests regardless of whether dom0 support was selected. > In case you are worrying about gnt devices, I'd be fine to switch to > > default XEN_BACKEND || XEN_GNTDEV Sure. maybe even: default XEN_BACKEND || XEN_GNTDEV || XEN_DOM0 Do you want me to resend with this changed or are you happy to fixup if there are no further comments? Thanks, Roger. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
