iommu.lists.linux-foundation.org archive mirror
 help / color / mirror / Atom feed
From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
	Jacob Pan <jacob.pan.linux@gmail.com>,
	Raj Ashok <ashok.raj@intel.com>,
	David Woodhouse <dwmw2@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	iommu@lists.linux-foundation.org,
	Jean-Philippe Brucker <jean-philippe@linaro.com>,
	Wu Hao <hao.wu@intel.com>
Subject: Re: [PATCH v2 4/9] iommu/ioasid: Add reference couting functions
Date: Tue, 25 Aug 2020 12:20:48 +0200	[thread overview]
Message-ID: <20200825102048.GB3252704@myrica> (raw)
In-Reply-To: <31af38ba-5cda-5d60-237e-f98cfc87da1b@linux.intel.com>

On Mon, Aug 24, 2020 at 10:26:55AM +0800, Lu Baolu wrote:
> Hi Jacob,
> 
> On 8/22/20 12:35 PM, Jacob Pan wrote:
> > There can be multiple users of an IOASID, each user could have hardware
> > contexts associated with the IOASID. In order to align lifecycles,
> > reference counting is introduced in this patch. It is expected that when
> > an IOASID is being freed, each user will drop a reference only after its
> > context is cleared.
> > 
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
[...]
> > +/**
> >    * ioasid_find - Find IOASID data
> >    * @set: the IOASID set
> >    * @ioasid: the IOASID to find
> 
> Do you need to increase the refcount of the found ioasid and ask the
> caller to drop it after use? Otherwise, the ioasid might be freed
> elsewhere.

ioasid_find() takes a getter function as parameter, which ensures that the
returned data is valid. It fetches the IOASID data under rcu_read_lock()
and calls the getter on the private data (for example mmget_not_zero() for
bare-metal SVA). Given that, I don't think returning with a reference to
the IOASID is necessary. The IOASID may be freed once ioasid_find()
returns but not the returned data.

Thanks,
Jean
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2020-08-25 10:21 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-22  4:35 [PATCH v2 0/9] IOASID extensions for guest SVA Jacob Pan
2020-08-22  4:35 ` [PATCH v2 1/9] docs: Document IO Address Space ID (IOASID) APIs Jacob Pan
2020-08-23  7:05   ` Lu Baolu
2020-08-28 17:01     ` Jacob Pan
2020-08-24 10:32   ` Jean-Philippe Brucker
2020-08-27 16:21     ` Auger Eric
2020-09-01 16:56       ` Jacob Pan
2020-09-07  8:03         ` Auger Eric
2020-09-08 17:29           ` Jacob Pan
2020-08-28 22:24     ` Jacob Pan
2020-08-22  4:35 ` [PATCH v2 2/9] iommu/ioasid: Rename ioasid_set_data() Jacob Pan
2020-08-24 18:29   ` Jean-Philippe Brucker
2020-09-01 11:51   ` Auger Eric
2020-08-22  4:35 ` [PATCH v2 3/9] iommu/ioasid: Introduce ioasid_set APIs Jacob Pan
2020-08-22 12:53   ` kernel test robot
2020-08-24  2:24   ` Lu Baolu
2020-09-01 21:28     ` Jacob Pan
2020-09-02  2:39       ` Lu Baolu
2020-08-24 18:28   ` Jean-Philippe Brucker
2020-08-24 18:30     ` Randy Dunlap
2020-09-02 21:46       ` Jacob Pan
2020-08-24 18:34     ` Randy Dunlap
2020-09-02 21:47       ` Jacob Pan
2020-09-02 21:44     ` Jacob Pan
2020-09-01 11:51   ` Auger Eric
2020-09-03 21:07     ` Jacob Pan
2020-09-07  8:04       ` Auger Eric
2020-08-22  4:35 ` [PATCH v2 4/9] iommu/ioasid: Add reference couting functions Jacob Pan
2020-08-24  2:26   ` Lu Baolu
2020-08-25 10:20     ` Jean-Philippe Brucker [this message]
2020-08-25 10:19   ` Jean-Philippe Brucker
2020-09-08 20:30     ` Jacob Pan
2020-09-01 12:13   ` Auger Eric
2020-09-08 20:49     ` Jacob Pan
2020-09-24 18:29   ` Shameerali Kolothum Thodi
2020-08-22  4:35 ` [PATCH v2 5/9] iommu/ioasid: Introduce ioasid_set private ID Jacob Pan
2020-08-22  8:36   ` kernel test robot
2020-08-22  9:03   ` kernel test robot
2020-08-25 10:22   ` Jean-Philippe Brucker
2020-09-08 22:19     ` Jacob Pan
2020-09-01 15:38   ` Auger Eric
2020-09-08 22:40     ` Jacob Pan
2020-09-10  9:18       ` Auger Eric
2020-08-22  4:35 ` [PATCH v2 6/9] iommu/ioasid: Introduce notification APIs Jacob Pan
2020-08-25 10:26   ` Jean-Philippe Brucker
2020-09-09 20:37     ` Jacob Pan
2020-09-01 16:49   ` Auger Eric
2020-09-09 22:58     ` Jacob Pan
2020-09-10  8:59       ` Auger Eric
2020-08-22  4:35 ` [PATCH v2 7/9] iommu/vt-d: Listen to IOASID notifications Jacob Pan
2020-09-01 17:03   ` Auger Eric
2020-09-10  4:54     ` Jacob Pan
2020-08-22  4:35 ` [PATCH v2 8/9] iommu/vt-d: Send IOASID bind/unbind notifications Jacob Pan
2020-08-22  4:35 ` [PATCH v2 9/9] iommu/vt-d: Store guest PASID during bind Jacob Pan
2020-09-01 17:08   ` Auger Eric
2020-09-10 17:12     ` Jacob Pan

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=20200825102048.GB3252704@myrica \
    --to=jean-philippe@linaro.org \
    --cc=ashok.raj@intel.com \
    --cc=baolu.lu@linux.intel.com \
    --cc=dwmw2@infradead.org \
    --cc=hao.wu@intel.com \
    --cc=iommu@lists.linux-foundation.org \
    --cc=jacob.pan.linux@gmail.com \
    --cc=jean-philippe@linaro.com \
    --cc=kevin.tian@intel.com \
    --cc=linux-kernel@vger.kernel.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 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).