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Subject: Re: [PATCH 2/2] virtio-console: remove unnecessary kmemdup()
To:     Xianting Tian <xianting.tian@linux.alibaba.com>,
        gregkh@linuxfoundation.org, amit@kernel.org, arnd@arndb.de
Cc:     linuxppc-dev@lists.ozlabs.org,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, osandov@fb.com
References: <20210801051655.79048-1-xianting.tian@linux.alibaba.com>
 <b5554967-a683-96ae-deb9-2d4980d33b41@kernel.org>
 <5ad81a0e-fbb2-a849-6db7-f5718633d282@linux.alibaba.com>
From:   Jiri Slaby <jirislaby@kernel.org>
Message-ID: <a2598ec9-7bc9-be42-bcab-fa19c9e734f7@kernel.org>
Date:   Mon, 2 Aug 2021 10:40:03 +0200
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On 02. 08. 21, 10:32, Xianting Tian wrote:
> 
> 在 2021/8/2 下午3:25, Jiri Slaby 写道:
>> Hi,
>>
>> why is this 2/2? I seem (Lore neither) to find 1/2.
> You didn't receive 1/2?
> [PATCH 1/2] tty: hvc: pass DMA capable memory to put_chars()
> https://lkml.org/lkml/2021/8/1/8 <https://lkml.org/lkml/2021/8/1/8>

Oh, I did, but it's not properly threaded. PLease fix your setup.

>> On 01. 08. 21, 7:16, Xianting Tian wrote:
>>> hvc framework will never pass stack memory to the put_chars() function,
>>
>> Am I blind or missing something?
>>
>> hvc_console_print(...)
>> {
>>   char c[N_OUTBUF]
>> ...
>>   cons_ops[index]->put_chars(vtermnos[index], c, i);
>>
>> The same here:
>>
>> hvc_poll_put_char(..., char ch)
>> {
>> ...
>>    n = hp->ops->put_chars(hp->vtermno, &ch, 1);
>>
>> AFAICS both of them *pass* a pointer to stack variable.
> 
> yes, I discussed the issue with Arnd before in below thread,  you can 
> get the history, thanks
> 
> https://lkml.org/lkml/2021/7/27/494 <https://lkml.org/lkml/2021/7/27/494>

So is this a v2? You should have noted that. And what changed from v1 too.

>>> So the calling of kmemdup() is unnecessary, remove it.
>>>
>>> Fixes: c4baad5029 ("virtio-console: avoid DMA from stack")
>>
>> This patch doesn't "Fix" -- it reverts the commit. You should've CCed 
>> the author too.
> 
> yes, we discussed ther issue in above thread, which we CCed the author.

I don't see any input from the author?


Anyway, 1/2 does not even build, so you will send v3 with all the above 
fixed, hopefully.

thanks,
-- 
js