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SubjectRe: [PATCH] ACPI, APEI: Fixup incorrect 16-bit access width firmware bug


On 07/21/2017 05:56 PM, Andy Shevchenko wrote:
> On Fri, Jul 21, 2017 at 12:41 PM, Song liwei <liwei.song@windriver.com> wrote:
>
>> [Firmware Bug]: APEI: Invalid bit width + offset in GAR [0xb2/16/0/1/1]
>>
>> This is due to an 8-bit access width is specified for a 16-bit register,
>> Do bit_width check just like what the original commit have done.
>
>> else if (bit_width == 64 && bit_offset == 0 && (*paddr & 0x07) == 0 &&
>> *access_bit_width < 64)
>> *access_bit_width = 64;
>> + else if (bit_width == 16 && bit_offset == 0 && (*paddr & 0x01) == 0 &&
>> + *access_bit_width < 16)
>> + *access_bit_width = 16;
>
> Wouldn't be better to rearrange that it will go in a sequence
> (16,32,64 or 64,32,16) ?
>
> or move bit_offset == 0 into external condion
>
> /* Fixup common BIOS bug */
> if (bit_offset == 0) {
> if (bit_width == 16 && (*paddr & 0x01) == 0 && *access_bit_width < 16)
> *access_bit_width = 16;
> else if (bit_width == 32 && (*paddr & 0x03) == 0 &&
> *access_bit_width < 32)
> *access_bit_width = 32;
> else if (bit_width == 64 && (*paddr & 0x07) == 0 &&
> *access_bit_width < 64)
> *access_bit_width = 64;
> }
>
>
> It might be (I'm not sure it will make it better, just a side note)
> considered to convert each internal conditional to
>
> ...if (bit_width == XX && (*paddr & YY) == 0)
> *access_bit_width = max(*access_bit_width, bit_width);

Hi Andy,

Thanks for your suggestion, what about the condition like the following?
The main bug in bios is bit_width is not comfortable with access_bit_width
So check it first.

if (*access_bit_width < bit_width && bit_offset == 0) {
if ((bit_width == 16 && (*paddr & 0x01) == 0) ||
(bit_width == 32 && (*paddr & 0x03) == 0) ||
(bit_width == 64 && (*paddr & 0x07) == 0))
*access_bit_width = bit_width;
}


Thanks,
Liwei.


>

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