+ Juergen, Boris On Fri, 30 Aug 2019, Christoph Hellwig wrote: > Can we take a step back and figure out what we want to do here? > > AFAICS this function allocates memory for the swiotlb-xen buffer, > and that means it must be <= 32-bit addressable to satisfy the DMA API > guarantees. That means we generally want to use GFP_DMA32 everywhere > that exists, but on systems with odd zones we might want to dip into > GFP_DMA. This also means swiotlb-xen doesn't actually do the right > thing on x86 at the moment. So shouldn't we just have one common > routine in swiotlb-xen.c that checks if we have CONFIG_ZONE_DMA32 > set, then try GFP_DMA32, and if not check if CONFIG_ZONE_DMA is set > and then try that, else default to GFP_KERNEL?
Yes, for ARM/ARM64 it makes a lot of sense given that dom0 is 1:1 mapped (pseudo-physical == physical). I'll let Juergen and Boris comment on the x86 side of things, but on x86 PV Dom0 is not 1:1 mapped so GFP_DMA32 is probably not meaningful. _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
