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[18.153.191.229]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a52bd85d51sm192467f8f.94.2025.06.04.20.55.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Jun 2025 20:55:25 -0700 (PDT) Message-ID: Date: Thu, 5 Jun 2025 11:55:20 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] iommu/vt-d: Remove dead code in intel_iommu_domain_alloc_paging_flags() To: Baolu Lu , Wei Wang , kevin.tian@intel.com, yi.l.liu@intel.com, dwmw2@infradead.org, jroedel@suse.de, linux-kernel@vger.kernel.org, iommu@lists.linux.dev References: <20250530091325.694456-1-wei.w.wang@intel.com> Content-Language: en-US From: Ethan Zhao In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 6/3/2025 10:39 AM, Baolu Lu wrote: > On 5/30/25 17:13, Wei Wang wrote: >> When dirty_tracking is enabled, first_stage is set to false to use the >> second stage translation table. dmar_domain->use_first_level, which is >> assigned from first_page, is guaranteed to be false when the execution >> reaches the location of the code to be removed by this patch. So the >> handling for dmar_domain->use_first_level being true there will never >> be executed. >> >> Signed-off-by: Wei Wang >> --- >>   drivers/iommu/intel/iommu.c | 7 +------ >>   1 file changed, 1 insertion(+), 6 deletions(-) >> >> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c >> index cb0b993bebb4..1145567c60f9 100644 >> --- a/drivers/iommu/intel/iommu.c >> +++ b/drivers/iommu/intel/iommu.c >> @@ -3418,13 +3418,8 @@ intel_iommu_domain_alloc_paging_flags(struct >> device *dev, u32 flags, >>           spin_lock_init(&dmar_domain->s1_lock); >>       } >> -    if (dirty_tracking) { >> -        if (dmar_domain->use_first_level) { > > This *explicit* check enforces that dirty tracking cannot be supported > for a domain that relies on first-stage translation due to the lack of > enabling/disabling dirty tracking support. > > While this might appear redundant, this prevents potential issues > if related code is modified without awareness of this dependency. There would always something sooner or later like this to stop the improper configuration/coding , under an assumption that caller path always coded perfect, indeed, we could remove a lot of error stopper code. But that world seems never works like that. Thanks, Ethan > >> -            iommu_domain_free(domain); >> -            return ERR_PTR(-EOPNOTSUPP); >> -        } > > Thanks, > baolu >