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SubjectRe: [PATCH] BISECTED x86: avoid qword access in memcpy_*io
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Yes, that would make sense.

"Hidetoshi Seto" <seto.hidetoshi@jp.fujitsu.com> wrote:

>(2010/07/21 11:48), H. Peter Anvin wrote:
>> On 07/20/2010 06:21 PM, Hidetoshi Seto wrote:
>>> With v2.6.35-rc5, my x86-64 server doesn't boot but reports a
>>> Completer Abort on lpfc card.
>>>
>>> The result of git-bisect is:
>>> 6175ddf06b6172046a329e3abfd9c901a43efd2e is the first bad commit
>>> commit 6175ddf06b6172046a329e3abfd9c901a43efd2e
>>> Author: Brian Gerst <brgerst@gmail.com>
>>> Date: Fri Feb 5 09:37:07 2010 -0500
>>> x86: Clean up mem*io functions.
>>>
>>> What I found are:
>>> - memcpy for 64bit uses movq if count >= 64 (arch/x86/lib/memcpy_64.S)
>>> - memcpy_toio and memcpy_fromio have changed to use this memcpy by
>>> the above commit.
>>> - my debug shows that lpfc calls memcpy_toio with not-qword-aligned
>>> addresses and count >= 64, e.g.:
>>> memcpy_toio(0xffffc900118de004, 0xffff88047293d614, 124);
>>> and it seems that it comes from:
>>> [drivers/scsi/lpfc/lpfc_sli.c]
>>> 4929 /* First copy mbox command data to HBA SLIM, skip past first
>>> 4930 word */
>>> 4931 to_slim = phba->MBslimaddr + sizeof (uint32_t);
>>> 4932 lpfc_memcpy_to_slim(to_slim, &mb->un.varWords[0],
>>> 4933 MAILBOX_CMD_SIZE - sizeof (uint32_t));
>>>
>>> Still I'm not sure what is wrong in software or hardware, however
>>> I suppose that qword access to iomem is not always safe, so it will
>>> be OK to back to use __inline_memcpy which uses movsl.
>>>
>>> I confirmed that my server (w/ lpfc) boots with 35-rc5 + this patch.
>>>
>>> Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
>>
>> A driver should not use the memcpy-like instructions if it isn't set up
>> to act as memory (meaning it can handle arbitrary byte enables.)
>
>So then is this a problem of lpfc driver?
>James, could you agree on that?
>
>> The function it should be using is called, fairly counterintuitively,
>> __iowrite32_copy(). It really should be called memcpy_toio32() or
>> something similar.
>>
>> -hpa
>
>It seems that lpfc already implemented lpfc_memcpy_{to,from}_slim()
>as such memcpy_*io32, but limited use of it to on big endian platforms
>only. Now lpfc can move to use it always, right?
>
>
>Thanks,
>H.Seto
>

--
Sent from my mobile phone. Please pardon any lack of formatting.


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