Messages in this thread | | | Subject | Re: [PATCH] EFI: Do not use __pa() to get the physical address of an ioremapped memory range | From | Matt Fleming <> | Date | Mon, 12 Sep 2011 15:52:10 +0100 |
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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.
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?
-- Matt Fleming, Intel Open Source Technology Center
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