Messages in this thread | | | Date | Wed, 21 Feb 2018 14:51:19 +0100 | From | Jonathan Neuschäfer <> | Subject | Re: [PATCH 1/6] powerpc/mm/32: Use pfn_valid to check if pointer is in RAM |
| |
Hello Christophe,
On Tue, Feb 20, 2018 at 06:45:09PM +0100, christophe leroy wrote: [...] > > - if (slab_is_available() && (p < virt_to_phys(high_memory)) && > > + if (slab_is_available() && pfn_valid(__phys_to_pfn(p)) && > > I'm not sure this is equivalent: > > high_memory = (void *) __va(max_low_pfn * PAGE_SIZE); > #define ARCH_PFN_OFFSET ((unsigned long)(MEMORY_START >> PAGE_SHIFT)) > #define pfn_valid(pfn) ((pfn) >= ARCH_PFN_OFFSET && (pfn) < max_mapnr) > set_max_mapnr(max_pfn); > > So in the current implementation it checks against max_low_pfn while your > patch checks against max_pfn > > max_low_pfn = max_pfn = memblock_end_of_DRAM() >> PAGE_SHIFT; > #ifdef CONFIG_HIGHMEM > max_low_pfn = lowmem_end_addr >> PAGE_SHIFT; > #endif
Good point, I haven't considered CONFIG_HIGHMEM before.
As far as I understand it, in the non-CONFIG_HIGHMEM case:
- max_low_pfn is set to the same value as max_pfn, so the ioremap check should detect the same PFNs as RAM.
and with CONFIG_HIGHMEM:
- max_low_pfn is set to lowmem_end_addr >> PAGE_SHIFT - but max_pfn isn't
So, I think you're right.
While looking through arch/powerpc/mm, I noticed that there's a page_is_ram function, which simply uses the memblocks directly, on PPC32. It seems like a good candidate for the RAM check in __ioremap_caller, except that there's this code, which apparently trashes memblock 0 completely on non-CONFIG_NEED_MULTIPLE_NODES:
https://elixir.bootlin.com/linux/v4.16-rc2/source/arch/powerpc/mm/mem.c#L223
Thanks, Jonathan Neuschäfer [unhandled content-type:application/pgp-signature] | |