Messages in this thread | | | Subject | Re: [PATCH v4 2/2] xen: add helpers to allocate unpopulated memory | From | Jürgen Groß <> | Date | Fri, 14 Aug 2020 12:27:32 +0200 |
| |
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.
Juergen
| |