Messages in this thread | | | Date | Thu, 15 Sep 2011 09:22:24 +0800 | Subject | Re: [PATCH] EFI: Do not use __pa() to get the physical address of an ioremapped memory range | From | Shaohua Li <> |
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2011/9/12 Matt Fleming <matt@console-pimps.org>: > On Fri, 2011-09-02 at 13:12 +0800, huang ying wrote: >> On Thu, Sep 1, 2011 at 8:28 PM, Matt Fleming <matt@console-pimps.org> wrote: >> > >> > Hmm.. does anyone know why we ioremap_cache() the memory on >> > CONFIG_X86_32 instead of ioremap_nocache()? In the case of >> > EFI_MEMORY_MAPPED_IO the memory really needs to be uncached. Then if >> > we've ioremap'd the memory we should skip set_memory_uc() altogether, >> > no? >> >> Because whether the mapping should be cached is determined by md->attr >> instead of md->type. And besides UC, we may add WC, etc support. > > Confused. > > The CONFIG_X86_64 version of efi_ioremap() looks like this, > > void __iomem *__init efi_ioremap(unsigned long phys_addr, unsigned long size, > u32 type) > { > unsigned long last_map_pfn; > > if (type == EFI_MEMORY_MAPPED_IO) > return ioremap(phys_addr, size); > > Which uses md->type to figure out if we should call ioremap(), which on > x86 is #define'd to ioremap_nocache(). CONFIG_X86_32 doesn't do this, > but it looks to me like it should. agree. mapping it wrong and fixing it later makes no sense. we should get the mapping correct at the first.
> Zhang, I agree that calling __pa() on an ioremap()'d region is bogus, > but I don't understand why no one is seeing this crash on x86-64. Is it > something to do with the x86-64 memory map layout such that __pa() works > on an ioremap()'d address? x86-64 does identity mapping for larger space (from 0 to the last physical mem even there is hole). Maybe this is the reason. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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