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Apr 2018 13:46:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amdcloud.onmicrosoft.com; s=selector1-amd-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=jnfBJs0OIVA+DwRzOl+7/Ae4jm9qtQsqqlhXwKagKco=; b=rDHIQVQ+Mi32ROLEt9ruE38RChaD8okXQrLiP9vpVa1kMYd5u4E9INDzW8Fq3KW2r8Yazp0WPIrd16+9gHQBBRqkqaB2c8xyiaR+cHMl5prfWZuVBHULf8vDx8wpNpewdcUXB0bPAGEdv59Ut71rtwSBDHST91E4dRr2mi9G5qE= Received: from [10.224.10.182] (165.204.77.1) by SN1PR12MB0701.namprd12.prod.outlook.com (2a01:111:e400:c42a::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384_P256) id 15.20.675.14; Tue, 17 Apr 2018 17:46:18 +0000 Subject: Re: [PATCH v3 1/2] iommu - Enable debugfs exposure of the IOMMU To: Gary R Hook , iommu@lists.linux-foundation.org Cc: linux-kernel@vger.kernel.org References: <152302042701.47565.17954813724758433858.stgit@sosxen2.amd.com> <152302066417.47565.4017200105445420643.stgit@sosxen2.amd.com> From: "Hook, Gary" Message-ID: 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linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/6/2018 9:17 AM, Gary R Hook wrote: > Provide base enablement for using debugfs to expose internal data of > an IOMMU driver. When called, create the /sys/kernel/debug/iommu > directory. Emit a strong warning at boot time to indicate that this > feature is enabled. > > This patch adds a top-level function that will create the (above) > directory, under which a driver may create a hw-specific directory for > its use. The function > > iommu_debugfs_setup() > > returns a pointer to the new dentry structure created for > /sys/kernel/debug/iommu, or NULL in the event of a failure. An IOMMU > driver should call this function first, and then create a directory > beneath it. A driver implementation might look something like: > > static struct dentry *my_debugfs; > > struct dentry *d_top; > if (!my_debugfs) { > d_top = iommu_debugfs_setup(); > if (d_top) > my_debugfs = debugfs_create_dir("vendor", d_top); > } > > Since the IOMMU driver can not be removed from the running system, this > patch only provides an "on" function. > > Signed-off-by: Gary R Hook > --- > drivers/iommu/Kconfig | 11 ++++++++ > drivers/iommu/Makefile | 1 + > drivers/iommu/iommu-debugfs.c | 58 +++++++++++++++++++++++++++++++++++++++++ > include/linux/iommu.h | 4 +++ > 4 files changed, 74 insertions(+) > create mode 100644 drivers/iommu/iommu-debugfs.c > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > index f3a21343e636..c1e39dabfec2 100644 > --- a/drivers/iommu/Kconfig > +++ b/drivers/iommu/Kconfig > @@ -60,6 +60,17 @@ config IOMMU_IO_PGTABLE_ARMV7S_SELFTEST > > endmenu > > +config IOMMU_DEBUG > + bool "Enable IOMMU internals in DebugFS" > + depends on DEBUG_FS > + default n > + help > + Allows exposure of IOMMU device internals. This option enables > + the use of debugfs by IOMMU drivers as required. Devices can, > + at initialization time, cause the IOMMU code to create a top-level > + debug/iommu directory, and then populate a subdirectory with > + entries as required. I should explicitly ask about this: Joerg had suggested IOMMU_DEBUGFS, but here I've changed to IOMMU_DEBUG. I'm not seeing a lot of CONFIG options that use DEBUGFS for debugfs options, so I chose to follow an implied convention. Question: should this indeed be IOMMU_DEBUGFS? ^^^^^^^^^^^^^