Messages in this thread | | | Subject | Re: [PATCH] EFI: Do not use __pa() to get the physical address of an ioremapped memory range | From | Zhang Rui <> | Date | Thu, 15 Sep 2011 09:52:15 +0800 |
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On Thu, 2011-09-15 at 09:22 +0800, Shaohua Li wrote: > 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. > So what kinds of memory regions need ioremap_nocache? should we make this decision based on the memory range type or attribute or even both of them?
-rui
> > 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.
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