Re: [Xen-devel] [PATCH] x86/setup: don't relocate the VGA hole

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 07/02/2013 20:20, "Ian Campbell" <ian.campbell@xxxxxxxxxx> wrote:

>> @@ -840,10 +839,8 @@ void __init __start_xen(unsigned long mb
>>               * data until after we have switched to the relocated
>> pagetables!
>>               */
>>              barrier();
>> -            dst = move_memory(e, 0, (unsigned long)&_end - XEN_VIRT_START,
>> 1);
>> -
>> -            /* Poison low 1MB to detect stray pointers to physical 0-1MB. */
>> -            memset(dst, 0x55, 1U << 20);
> 
> Is this poisoning not still desirable?

If we don't copy that low 1MB I don't see any reason to poison it at the
destination.

>> +            move_memory(e + (1u << 20), (1u << 20),
>> +                      ((unsigned long)&_end - XEN_VIRT_START) - (1u << 20),
>> 1);

1MB here is actually something of a magic number. We could make use of
_start instead, eg:

off = (ulong)&_start - XEN_VIRT_START;
move_memory(e + off, off, (ulong)&_end - (ulong)&_start, 1);

This would be my preference.

 -- Keir

> 
> 
> 
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