[alsa-devel] [PATCH 1/1] ALSA: intel8x0: Improve comments for VM optimization
tiwai at suse.de
Tue Nov 8 07:51:50 CET 2011
At Mon, 7 Nov 2011 20:33:25 +0400,
Denis V. Lunev wrote:
> The recently merged 228cf79376f1 looks a bit hackish while it is not.
> The change was quite simple. In a virtualized environment the
> patch unhacks old kludge introduced for old broken AC97 hardware.
> This patch adds proper comment to "unkludge" code.
> Signed-off-by: Denis V. Lunev <den at openvz.org>
> Signed-off-by: Konstantin Ozerkov <kozerkov at parallels.com>
Applied now. Thanks.
> sound/pci/intel8x0.c | 7 +++++++
> 1 files changed, 7 insertions(+), 0 deletions(-)
> diff --git a/sound/pci/intel8x0.c b/sound/pci/intel8x0.c
> index 29e3125..c3b9bd0 100644
> --- a/sound/pci/intel8x0.c
> +++ b/sound/pci/intel8x0.c
> @@ -1077,6 +1077,13 @@ static snd_pcm_uframes_t snd_intel8x0_pcm_pointer(struct snd_pcm_substream *subs
> if (civ != igetbyte(chip, ichdev->reg_offset + ICH_REG_OFF_CIV))
> + /* IO read operation is very expensive inside virtual machine
> + * as it is emulated. The probability that subsequent PICB read
> + * will return different result is high enough to loop till
> + * timeout here.
> + * Same CIV is strict enough condition to be sure that PICB
> + * is valid inside VM on emulated card. */
> if (chip->inside_vm)
> if (ptr1 == igetword(chip, ichdev->reg_offset + ichdev->roff_picb))
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