linux-kernel - Re: BUG() at boot in __phys_addr with DEBUG

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Date:	Thu, 13 Nov 2014 13:08:03 +0000
From:	Matt Fleming <matt.fleming@...el.com>
To:	Dave Hansen <dave.hansen@...el.com>
CC:	Borislav Petkov <bp@...e.de>,
	the arch/x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: BUG() at boot in __phys_addr with DEBUG_VIRTUAL

On Wed, 2014-11-12 at 07:20 -0800, Dave Hansen wrote:
> 
> The path that we're actually hitting this from is:
> 
> > __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long
> ...
> >         if (pfn_range_is_mapped(PFN_DOWN(__pa(address)),
> >                                 PFN_DOWN(__pa(address)) + 1))
> >                 split_page_count(level);

I'm sure I'm just being dumb, but I can't for the life of me work out
why we need to calculate the physical address from the virtual address
at this point - we should already have that information.

> So perhaps efi_map_region() is handing an address from the EFI identity
> map down in here.  __pa() gets called on it, but that fails since __pa()
> only works on the *KERNEL* identity map.

Yep, sounds right.

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