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SubjectRe: [PATCH 4/6] x86: fix some bugs about EFI runtime code mapping
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On Fri, 2008-01-25 at 10:16 +0100, Ingo Molnar wrote:
> * Huang, Ying <ying.huang@intel.com> wrote:
>
> > This patch fixes some bugs of making EFI runtime code executable.
> >
> > - Use change_page_attr in i386 too. Because the runtime code may be
> > mapped not through ioremap.
> >
> > - If there is no _PAGE_NX in __supported_pte_mask, the change_page_attr
> > is not called.
> >
> > - Make efi_ioremap map pages as PAGE_KERNEL_EXEC, because EFI runtime
> > code may be mapped through efi_ioremap.
>
> thanks, applied.
>
> note that here:
>
> > - set_fixmap_nocache(FIX_EFI_IO_MAP_FIRST_PAGE - pages_mapped,
> > - offset);
> > + __set_fixmap(FIX_EFI_IO_MAP_FIRST_PAGE - pages_mapped,
> > + offset, PAGE_KERNEL_EXEC);
>
> you've changed it from nocache-noexec to cached-exec. I suspect that's
> what we want - except if an early EFI area can be non-prefetchable
> device memory. Can that ever happen? Would you like to have
> PAGE_KERNEL_NOCACHE_EXEC perhaps? I implemented that yesterday but did
> not commit it yet. (see the patch below)

Yes. EFI area can be non-prefetchable device memory. I should use
PAGE_KERNEL_NOCACHE_EXEC.

A question about this:

The MTRR on x86 should have set the memory area as un-cachable. Why do
we bother to set it in page table?

Best Regards,
Huang Ying



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