RE: [PATCH] arm: xen: mm: use __GPF_DMA32 for arm64
From: Peng Fan
Date: Tue Aug 27 2019 - 21:48:26 EST
Hi Robin,
> Subject: Re: [PATCH] arm: xen: mm: use __GPF_DMA32 for arm64
>
> On 09/07/2019 09:22, Peng Fan wrote:
> > arm64 shares some code under arch/arm/xen, including mm.c.
> > However ZONE_DMA is removed by commit
> > ad67f5a6545("arm64: replace ZONE_DMA with ZONE_DMA32").
> > So to ARM64, need use __GFP_DMA32.
> >
> > Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
> > ---
> > arch/arm/xen/mm.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c index
> > e1d44b903dfc..a95e76d18bf9 100644
> > --- a/arch/arm/xen/mm.c
> > +++ b/arch/arm/xen/mm.c
> > @@ -27,7 +27,7 @@ unsigned long xen_get_swiotlb_free_pages(unsigned
> > int order)
> >
> > for_each_memblock(memory, reg) {
> > if (reg->base < (phys_addr_t)0xffffffff) {
> > - flags |= __GFP_DMA;
> > + flags |= __GFP_DMA | __GFP_DMA32;
>
> Given the definition of GFP_ZONE_BAD, I'm not sure this combination of flags
> is strictly valid, but rather is implicitly reliant on only one of those zones ever
> actually existing. As such, it seems liable to blow up if the plans to add
> ZONE_DMA to arm64[1] go ahead.
How about this, or do you have any suggestions?
diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
index d33b77e9add3..f61c29a4430f 100644
--- a/arch/arm/xen/mm.c
+++ b/arch/arm/xen/mm.c
@@ -28,7 +28,11 @@ unsigned long xen_get_swiotlb_free_pages(unsigned int order)
for_each_memblock(memory, reg) {
if (reg->base < (phys_addr_t)0xffffffff) {
+#ifdef CONFIG_ARM64
+ flags |= __GFP_DMA32;
+#else
flags |= __GFP_DMA;
+#endif
break;
}
}
Thanks,
Peng.
>
> Robin.
>
> [1]
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.ke
> rnel.org%2Flinux-arm-kernel%2F20190820145821.27214-1-nsaenzjulienne%
> 40suse.de%2F&data=02%7C01%7Cpeng.fan%40nxp.com%7C5d2a641b1
> e3f449562f908d72ae95d85%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0
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> XbEjiv4%2FZ9pYwTQTWxY%3D&reserved=0
>
> > break;
> > }
> > }
> >