linux-kernel - RE: [PATCH v2 4/6] iommu/vt-d: Remove unnecessary check in intel_iommu

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Date:   Thu, 7 Jul 2022 01:01:49 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        "Steve Wahl" <steve.wahl@....com>
CC:     David Woodhouse <dwmw2@...radead.org>,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        Mike Travis <mike.travis@....com>,
        Dimitri Sivanich <sivanich@....com>,
        "Anderson, Russ" <russ.anderson@....com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 4/6] iommu/vt-d: Remove unnecessary check in
 intel_iommu_add()

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Saturday, July 2, 2022 9:56 AM
> 
> The Intel IOMMU hot-add process starts from dmar_device_hotplug(). It
> uses the global dmar_global_lock to synchronize all the hot-add and
> hot-remove paths. In the hot-add path, the new IOMMU data structures
> are allocated firstly by dmar_parse_one_drhd() and then initialized by
> dmar_hp_add_drhd(). All the IOMMU units are allocated and initialized
> in the same synchronized path. There is no case where any IOMMU unit
> is created and then initialized for multiple times.
> 
> This removes the unnecessary check in intel_iommu_add() which is the
> last reference place of the global IOMMU array.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>

Reviewed-by: Kevin Tian <kevin.tian@...el.com>