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From: "Yang, Shunyong" <shunyong.yang@hxt-semitech.com>
To: "sohil.mehta@intel.com" <sohil.mehta@intel.com>,
	"gary.hook@amd.com" <gary.hook@amd.com>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	"ghook@amd.com" <ghook@amd.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 2/2] iommu/amd: Add basic debugfs infrastructure for AMD IOMMU
Date: Wed, 18 Apr 2018 05:58:48 +0000	[thread overview]
Message-ID: <1524031122.4031.5.camel@hxt-semitech.com> (raw)
In-Reply-To: <efa2b7a3-04a7-20b1-3651-89ebafa85c27@amd.com>

Hi, Gary and Sohil,

On Tue, 2018-04-17 at 13:38 -0400, Hook, Gary wrote:
> On 4/13/2018 8:08 PM, Mehta, Sohil wrote:
> > 
> > On Fri, 2018-04-06 at 08:17 -0500, Gary R Hook wrote:
> > > 
> > >   
> > > +
> > > +void amd_iommu_debugfs_setup(struct amd_iommu *iommu)
> > > +{
> > > +	char name[MAX_NAME_LEN + 1];
> > > +	struct dentry *d_top;
> > > +
> > > +	if (!debugfs_initialized())
> > Probably not needed.
> Right.

When will this check is needed?
IMO, this function is to check debugfs ready status before we want to
use debugfs. I just want to understand when we should use
debugfs_initialized();

Thanks.
Shunyong.

> 
> > 
> > 
> > > 
> > > +		return;
> > > +
> > > +	mutex_lock(&amd_iommu_debugfs_lock);
> > > +	if (!amd_iommu_debugfs) {
> > > +		d_top = iommu_debugfs_setup();
> > > +		if (d_top)
> > > +			amd_iommu_debugfs =
> > > debugfs_create_dir("amd", d_top);
> > > +	}
> > > +	mutex_unlock(&amd_iommu_debugfs_lock);
> > 
> > You can do the above only once if you iterate over the IOMMUs here
> >   instead of doing it in amd_iommu_init.
> I'm not sure it matters, given the finite number of IOMMUs in a
> system, 
> and the fact that this work is done exactly once. However, removal of
> a 
> lock is fine thing, so I'll move this around.
> 
> > 
> > 
> > > 
> > > +	if (amd_iommu_debugfs) {
> > > +		snprintf(name, MAX_NAME_LEN, "iommu%02d", iommu-
> > > > 
> > > > index);
> > > +		iommu->debugfs = debugfs_create_dir(name,
> > > +						    amd_iommu_de
> > > bugf
> > > s);
> > > +		if (!iommu->debugfs) {
> > > +			debugfs_remove_recursive(amd_iommu_debug
> > > fs);
> > > +			amd_iommu_debugfs = NULL;
> > > +		}
> > > +	}
> > > +}
> > -Sohil
> > 
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2018-04-18  6:15 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-06 13:17 [PATCH v3 0/2] Base enablement of IOMMU debugfs support Gary R Hook
2018-04-06 13:17 ` [PATCH v3 1/2] iommu - Enable debugfs exposure of the IOMMU Gary R Hook
2018-04-13 23:55   ` Mehta, Sohil
2018-04-17 17:36     ` Hook, Gary
2018-04-17 17:55       ` Robin Murphy
2018-04-17 18:06         ` Hook, Gary
2018-04-17 17:46   ` Hook, Gary
2018-04-17 18:13     ` Robin Murphy
2018-04-06 13:17 ` [PATCH v3 2/2] iommu/amd: Add basic debugfs infrastructure for AMD IOMMU Gary R Hook
2018-04-14  0:08   ` Mehta, Sohil
2018-04-17 17:38     ` Hook, Gary
2018-04-18  5:58       ` Yang, Shunyong [this message]
2018-04-18  7:27         ` Mehta, Sohil
2018-04-18  8:31           ` Yang, Shunyong
2018-04-18 20:16             ` Mehta, Sohil
2018-04-18 20:51               ` Hook, Gary
2018-04-19  1:52                 ` Yang, Shunyong
2018-04-30 19:57       ` Gary R Hook
2018-04-17  0:52   ` Mehta, Sohil
2018-04-17 17:42     ` Hook, Gary
2018-04-17 18:05       ` Robin Murphy

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