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From: Will Deacon <will.deacon@arm.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: "iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>, Kukjin Kim <kgene@kernel.org>,
	David Woodhouse <dwmw2@infradead.org>,
	Heiko Stuebner <heiko@sntech.de>, Hiroshi Doyu <hdoyu@nvidia.com>,
	Thierry Reding <thierry.reding@gmail.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	Arnd Bergmann <arnd@arndb.de>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Robin Murphy <Robin.Murphy@arm.com>,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	"jroedel@suse.de" <jroedel@suse.de>
Subject: Re: [PATCH 3/5] iommu: Limit iommu_attach/detach_device to devices with their own group
Date: Mon, 2 Feb 2015 16:45:46 +0000	[thread overview]
Message-ID: <20150202164545.GH31847@arm.com> (raw)
In-Reply-To: <20150130122814.GC3702@8bytes.org>

On Fri, Jan 30, 2015 at 12:28:14PM +0000, Joerg Roedel wrote:
> On Wed, Jan 28, 2015 at 02:35:24PM +0000, Will Deacon wrote:
> > On Tue, Jan 27, 2015 at 12:08:57AM +0000, Joerg Roedel wrote:
> > > @@ -51,6 +51,7 @@ struct iommu_group {
> > >  	void (*iommu_data_release)(void *iommu_data);
> > >  	char *name;
> > >  	int id;
> > > +	unsigned dev_cnt;
> > 
> > Is this actually used on a fast path, or can we just inspect the list of
> > devices on the group instead?
> 
> Not really a fast path, but we have to hold the group mutex while
> traversing the list, which could hurt performance somewhere else. Are
> these 4 bytes a problem?

No problem, it just seemed a bit redundant to have two ways of describing
the same thing and having the pain of keeping them in sync with each other.

Will

  reply	other threads:[~2015-02-02 16:45 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-27  0:08 [RFC PATCH 0/5] iommu: Introduce default domains for iommu groups Joerg Roedel
2015-01-27  0:08 ` [PATCH 1/5] iommu: Add default domain to iommu-groups Joerg Roedel
2015-01-27  0:08 ` [PATCH 2/5] iommu: Allocate a default domain for iommu groups Joerg Roedel
2015-01-28 14:30   ` Will Deacon
2015-01-28 15:11     ` Robin Murphy
2015-01-30 12:25     ` Joerg Roedel
2015-01-27  0:08 ` [PATCH 3/5] iommu: Limit iommu_attach/detach_device to devices with their own group Joerg Roedel
2015-01-28 14:35   ` Will Deacon
2015-01-30 12:28     ` Joerg Roedel
2015-02-02 16:45       ` Will Deacon [this message]
2015-02-03 12:25   ` Thierry Reding
2015-02-03 12:59     ` Joerg Roedel
2015-01-27  0:08 ` [PATCH 4/5] iommu: Make sure a device is always attached to a domain Joerg Roedel
2015-01-28 14:38   ` Will Deacon
2015-01-30 12:29     ` Joerg Roedel
2015-01-27  0:08 ` [PATCH 5/5] iommu: Add iommu_get_domain_for_dev function Joerg Roedel

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