linux-kernel - Re: [PATCH 1/3] x86, mm: Include the entire kernel memory map in trampoline

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Message-ID: <506DFAD8.5060701@zytor.com>
Date:	Thu, 04 Oct 2012 14:08:40 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jan Beulich <jbeulich@...e.com>
CC:	matt@...sole-pimps.org, linux-kernel@...r.kernel.org,
	matt.fleming@...el.com, mingo@...nel.org, x86@...nel.org,
	mjg@...hat.com, linux-efi@...r.kernel.org
Subject: Re: [PATCH 1/3] x86, mm: Include the entire kernel memory map in
 trampoline_pgd

On 10/03/2012 06:31 AM, Jan Beulich wrote:
>>>> Matt Fleming <matt@...sole-pimps.org> 10/03/12 2:59 PM >>>
>> +static int insert_identity_mapping(resource_size_t paddr, unsigned long vaddr,
>> +                    unsigned long size)
>> +{
>> +    unsigned long end = vaddr + size;
>> +    unsigned long next;
>> +    pgd_t *vpgd, *ppgd;
>> +
>> +#ifdef CONFIG_X86_32
>> +    ppgd = initial_page_table + pgd_index(paddr);
>> +
>> +    if (paddr >= PAGE_OFFSET || paddr + size > PAGE_OFFSET)
>> +        return 1;
>> +#else
>> +    ppgd = __va(real_mode_header->trampoline_pgd) + pgd_index(paddr);
>
> Missing equivalent code (to the 32-bit one above) here - after all, you're trying
> to potentially insert a 52-bit physical address into 48-bit virtual space.
>

We should have the check, but at least for Linux support we require
P <= V-2.

	-hpa


-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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