linux-kernel - RE: [PATCH v3 11/11] iommu/vt-d: Convert global spinlock into per domain lock

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Date:   Fri, 1 Jul 2022 08:18:48 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>
CC:     "Raj, Ashok" <ashok.raj@...el.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 11/11] iommu/vt-d: Convert global spinlock into per
 domain lock

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Wednesday, June 29, 2022 3:47 PM
> 
> Using a global device_domain_lock spinlock to protect per-domain device
> tracking lists is an inefficient way, especially considering this lock
> is also needed in the hot paths. This optimizes the locking mechanism
> by converting the global lock to per domain lock.
> 
> On the other hand, as the device tracking lists are never accessed in
> any interrupt context, there is no need to disable interrupts while
> spinning. Replace irqsave variant with spinlock calls.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>

except the previous comment on where to convert spin_lock_irqsave()
the rest looks good to me.

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