From: Joerg Roedel <jroedel@suse.de>
To: Shaohua Li <shli@fb.com>
Cc: linux-kernel@vger.kernel.org, gang.wei@intel.com,
hpa@linux.intel.com, mingo@kernel.org, kernel-team@fb.com,
ning.sun@intel.com, srihan@fb.com, alex.eydelberg@intel.com
Subject: Re: [PATCH V2] x86/tboot: add an option to disable iommu force on
Date: Wed, 26 Apr 2017 23:59:36 +0200 [thread overview]
Message-ID: <20170426215936.GT5077@suse.de> (raw)
In-Reply-To: <1c2cadcf5cd7d19cea93c56435610e61b551bd1e.1493223474.git.shli@fb.com>
On Wed, Apr 26, 2017 at 09:18:35AM -0700, Shaohua Li wrote:
> IOMMU harms performance signficantly when we run very fast networking
> workloads. It's 40GB networking doing XDP test. Software overhead is
> almost unaware, but it's the IOTLB miss (based on our analysis) which
> kills the performance. We observed the same performance issue even with
> software passthrough (identity mapping), only the hardware passthrough
> survives. The pps with iommu (with software passthrough) is only about
> ~30% of that without it. This is a limitation in hardware based on our
> observation, so we'd like to disable the IOMMU force on, but we do want
> to use TBOOT and we can sacrifice the DMA security bought by IOMMU. I
> must admit I know nothing about TBOOT, but TBOOT guys (cc-ed) think not
> eabling IOMMU is totally ok.
>
> So introduce a new boot option to disable the force on. It's kind of
> silly we need to run into intel_iommu_init even without force on, but we
> need to disable TBOOT PMR registers. For system without the boot option,
> nothing is changed.
>
> Signed-off-by: Shaohua Li <shli@fb.com>
Applied, thanks.
next prev parent reply other threads:[~2017-04-26 21:59 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-26 16:18 [PATCH V2] x86/tboot: add an option to disable iommu force on Shaohua Li
2017-04-26 21:59 ` Joerg Roedel [this message]
2017-04-27 6:52 ` Ingo Molnar
2017-04-28 22:07 ` Joerg Roedel
2017-04-27 6:51 ` Ingo Molnar
2017-04-27 8:42 ` Joerg Roedel
2017-04-27 14:49 ` Shaohua Li
2017-04-27 15:18 ` Joerg Roedel
2017-04-27 15:41 ` Shaohua Li
2017-04-27 16:04 ` Joerg Roedel
2017-05-05 6:59 ` Ingo Molnar
2017-05-05 8:40 ` Joerg Roedel
2017-05-06 9:48 ` Ingo Molnar
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=20170426215936.GT5077@suse.de \
--to=jroedel@suse.de \
--cc=alex.eydelberg@intel.com \
--cc=gang.wei@intel.com \
--cc=hpa@linux.intel.com \
--cc=kernel-team@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=ning.sun@intel.com \
--cc=shli@fb.com \
--cc=srihan@fb.com \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).