All of lore.kernel.org
 help / color / mirror / Atom feed
From: Rodrigo Vivi <rodrigo.vivi@intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] drm/i915/selftests: Provide full mb() around clflush
Date: Fri, 6 Jul 2018 13:31:56 -0700	[thread overview]
Message-ID: <20180706203156.GD23473@intel.com> (raw)
In-Reply-To: <153090886221.7594.9469545348039815576@cwilso3-mobl.ger.corp.intel.com>

On Fri, Jul 06, 2018 at 09:27:47PM +0100, Chris Wilson wrote:
> Quoting Rodrigo Vivi (2018-07-06 21:23:00)
> > On Fri, Jul 06, 2018 at 06:49:26PM +0100, Chris Wilson wrote:
> > > clflush is an unserialised instruction and the IA manual strongly advises
> > > you to serialise it with a mb. To be cautious, apply one before and one
> > > after,
> > 
> > my understanding is that we need one before and one after anyways,
> > not just a matter of being cautious for being cautious..
> > 
> > Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> 
> If you are really careful, you can reduce it to a mb between writes and
> the clflush; and vice verse, the mb between clflush and subsequent
> reads. It's all about prevent the clflush from overtaking or being
> overtaken by the operations it is meant to flush or invalidate
> respectively.
> 
> But since we're being paranoid here, do both.

hm... makes sense... better to be paranoid...

> -Chris
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

  reply	other threads:[~2018-07-06 20:32 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-06 17:49 [PATCH] drm/i915/selftests: Provide full mb() around clflush Chris Wilson
2018-07-06 17:56 ` ✗ Fi.CI.CHECKPATCH: warning for " Patchwork
2018-07-06 18:14 ` ✓ Fi.CI.BAT: success " Patchwork
2018-07-06 20:23 ` [PATCH] " Rodrigo Vivi
2018-07-06 20:27   ` Chris Wilson
2018-07-06 20:31     ` Rodrigo Vivi [this message]
2018-07-07 18:32 ` ✓ Fi.CI.IGT: success for " Patchwork

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180706203156.GD23473@intel.com \
    --to=rodrigo.vivi@intel.com \
    --cc=chris@chris-wilson.co.uk \
    --cc=intel-gfx@lists.freedesktop.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.