[alsa-devel] 答复: A bug about cache inconsistency report

[Takashi Iwai]

On Tue, 31 Jul 2018 15:51:06 +0200,
Hans Hu(SH-RD) wrote:
> 
> I did the test and Oops report when install driver( both snoop and non-snoop mode)

I don't understand.  Did my one-liner change the behavior or not?


thanks,

Takashi

> 
> -----邮件原件-----
> 发件人: Takashi Iwai [mailto:tiwai at suse.de]
> 发送时间: 31 July 2018 19:59
> 收件人: Hans Hu(SH-RD) <HansHu at zhaoxin.com>
> 抄送: 'alsa-devel at alsa-project.org' <alsa-devel at alsa-project.org>
> 主题: Re: [alsa-devel] A bug about cache inconsistency report
> 
> On Tue, 31 Jul 2018 12:52:04 +0200,
> Hans Hu(SH-RD) wrote:
> >
> > Hi All,
> >
> >                Try send an email.
> >
> >                Appearance:
> > when use non-snoop + ioctl path combination, an issue occurs:
> > usage: aplay -D plughw:0,0 44100_S16_LE_2c.wav Ubuntu, it performance
> > intermittently noise;
> >
> > Root case:
> >                Function set_pages_array_wc marked the PTE of the original address; Function set_memory_wc marked the PTE both original and after vmaped address.
> > [cid:image002.png at 01D428FF.92621520]
> > However, cache or not in transmission process is based on the PTE of the later, and the set_pages_array_wc did't mark it, so a cache inconsistency issue occurs.
> >
> >                Related bug:
> >                SHA1 ID: 9ddf1aeb2134e72275c97a2c6ff2e3eb04f2f27a
> 
> OK, so did you confirm that dropping the SG buffer support "fixes" the noise problem on your system?  The easiest test would be like:
> 
> --- a/sound/pci/hda/hda_controller.c
> +++ b/sound/pci/hda/hda_controller.c
> @@ -770,7 +770,7 @@ int snd_hda_attach_pcm_stream(struct hda_bus *_bus, struct hda_codec *codec,
>  size = CONFIG_SND_HDA_PREALLOC_SIZE * 1024;
>  if (size > MAX_PREALLOC_SIZE)
>  size = MAX_PREALLOC_SIZE;
> -snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV_SG,
> +snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV,
>        chip->card->dev,
>        size, MAX_PREALLOC_SIZE);
>  return 0;
> 
> 
> thanks,
> 
> Takashi
> 
> 
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