linux-kernel - Re: [PATCH v2 06/12] iommu/vt-d: Cleanup intel_context_flush

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Message-ID: <51cb2ef8-3cce-4af7-b6ce-c3e3d490e6a3@linux.intel.com>
Date: Wed, 5 Mar 2025 10:21:24 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Yi Liu <yi.l.liu@...el.com>, Joerg Roedel <joro@...tes.org>,
 Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
 Jason Gunthorpe <jgg@...pe.ca>, Kevin Tian <kevin.tian@...el.com>
Cc: Dave Jiang <dave.jiang@...el.com>, Vinod Koul <vkoul@...nel.org>,
 Fenghua Yu <fenghuay@...dia.com>, Zhangfei Gao <zhangfei.gao@...aro.org>,
 Zhou Wang <wangzhou1@...ilicon.com>, iommu@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 06/12] iommu/vt-d: Cleanup
 intel_context_flush_present()

On 3/4/25 16:43, Yi Liu wrote:
> On 2025/2/24 13:16, Lu Baolu wrote:
>> The intel_context_flush_present() is called in places where either the
>> scalable mode is disabled, or scalable mode is enabled but all PASID
>> entries are known to be non-present. In these cases, the flush_domains
>> path within intel_context_flush_present() will never execute. This dead
>> code is therefore removed.
> 
> The reason for this path is the remaining caller of
> intel_context_flush_present() is only the domain_context_clear_one() which
> is called in legacy mode path. Is it?
> If so, it seems unnecessary to keep __context_flush_dev_iotlb(info); in the
> end of the new intel_context_flush_present(). Also, since this helper is 
> more for legacy mode, might be good to move it out of pasid.c.:)

This helper is for invalidating various caches when a context entry is
present and certain fields are changed. It is used in both legacy and
scalable modes.

In the past, this helper would work even if some PASIDs were still in
use. After the changes introduced in this series, this PASID-in-use case
is removed. So remove the dead code.

Thanks,
baolu