On Thu, 2019-08-01 at 17:07 +0100, Robin Murphy wrote: > On 2019-08-01 4:44 pm, Nicolas Saenz Julienne wrote: > > On Wed, 2019-07-31 at 18:07 +0100, Catalin Marinas wrote: > > > On Wed, Jul 31, 2019 at 05:47:48PM +0200, Nicolas Saenz Julienne wrote: > > > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > > > > index 1c4ffabbe1cb..f5279ef85756 100644 > > > > --- a/arch/arm64/mm/init.c > > > > +++ b/arch/arm64/mm/init.c > > > > @@ -50,6 +50,13 @@ > > > > s64 memstart_addr __ro_after_init = -1; > > > > EXPORT_SYMBOL(memstart_addr); > > > > > > > > +/* > > > > + * We might create both a ZONE_DMA and ZONE_DMA32. ZONE_DMA is needed > > > > if > > > > there > > > > + * are periferals unable to address the first naturally aligned 4GB of > > > > ram. > > > > + * ZONE_DMA32 will be expanded to cover the rest of that memory. If > > > > such > > > > + * limitations doesn't exist only ZONE_DMA32 is created. > > > > + */ > > > > > > Shouldn't we instead only create ZONE_DMA to cover the whole 32-bit > > > range and leave ZONE_DMA32 empty? Can__GFP_DMA allocations fall back > > > onto ZONE_DMA32? > > > > Hi Catalin, thanks for the review. > > > > You're right, the GFP_DMA page allocation will fail with a nasty dmesg error > > if > > ZONE_DMA is configured but empty. Unsurprisingly the opposite situation is > > fine > > (GFP_DMA32 with an empty ZONE_DMA32). > > Was that tested on something other than RPi4 with more than 4GB of RAM? > (i.e. with a non-empty ZONE_NORMAL either way) No, all I did is play around with RPi4's memory size (1 GB vs 4 GB). I'll see If I can get access to a dts based board with more than 4 GB, If not I'll try to fake it. It's not ideal but I can set the limit on 3 GB and have the 3 areas created (with and witouth an empty ZONE_DMA32). On top of that, now that you ask, I realise I neglected all the ACPI based servers. I have access to some so I'll make sure I test everything on them too for the next series. Regards, Nicolas
Attachment:
signature.asc
Description: This is a digitally signed message part
