linux-kernel - Re: [PATCH] [8/8] RFC: Fix some EFI problems

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Date:	Tue, 12 Feb 2008 21:04:06 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andi Kleen <ak@...e.de>
cc:	ying.huang@...el.com, mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [8/8] RFC: Fix some EFI problems

On Mon, 11 Feb 2008, Andi Kleen wrote:

> >From code review the EFI memory map handling has a couple of problems:
> 
> - The test for _WB memory was reversed so it would set cache able memory
> to uncached
> - It would always set a wrong uninitialized zero address to uncached
> (so I suspect it always set the first few pages in phys memory to uncached,
> that is why it may have gone unnoticed) 
> - It would call set_memory_x() on a fixmap address that it doesn't
> handle correct.
> - Some other problems I commented in the code (but was unable to solve
> for now) 
> 
> I changed the ioremaps to set the correct caching attributes
> and also corrected the ordering so it looks roughly correct now.

The only effective change is:

-               if (md->attribute & EFI_MEMORY_WB)
+               if (!(md->attribute & EFI_MEMORY_WB))

I appreciate that you noticed the reverse logic, which I messed up
when I fixed up rejects.

I pulled this out as it is a real fix. The rest of this patch is just
turning code in circles for nothing, simply because it is functionally
completely irrelevant whether does simply:

        if ((end >> PAGE_SHIFT) <= max_pfn_mapped)
                va = __va(md->phys_addr);
        else
                va = efi_ioremap(md->phys_addr, size);

       if (!(md->attribute & EFI_MEMORY_WB))
                set_memory_uc(md->virt_addr, size);
or

       if ((end >> PAGE_SHIFT) <= max_pfn_mapped) {
                va = __va(md->phys_addr);

                if (!(md->attribute & EFI_MEMORY_WB))
                        set_memory_uc(md->virt_addr, size);
       } else
                va = efi_ioremap(md->phys_addr, size,
                                 !!(md->attribute & EFI_MEMORY_WB));

And you just copied the real bug in that logic as well:

          set_memory_uc(md->virt_addr, size);
------------------------^^^^^^^^

which is initialized a couple of lines down.

	md->virt_addr = (u64) (unsigned long) va;

The reordering/optimizing needs to be a separate patch.

Please keep bugfixes and other changes separate.
 
> +		/* RED-PEN does not handle overlapped areas */

Can you please use CHECKME/FIXME which is used everywhere else. No need to
invent an extra marker.

Thanks,

	tglx
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