Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <b3fef8c7-29d2-e1d3-09c9-7bb97510faf0@arm.com>
Date:   Tue, 23 May 2023 13:16:40 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:102.0) Gecko/20100101
 Thunderbird/102.11.0
Subject: Re: [PATCH v9 5/6] iommu/dma: Allow a single FQ in addition to
 per-CPU FQs
Content-Language: en-GB
To:     Niklas Schnelle <schnelle@linux.ibm.com>,
        Joerg Roedel <joro@8bytes.org>,
        Matthew Rosato <mjrosato@linux.ibm.com>,
        Will Deacon <will@kernel.org>,
        Wenjia Zhang <wenjia@linux.ibm.com>,
        Jason Gunthorpe <jgg@ziepe.ca>
Cc:     Gerd Bayer <gbayer@linux.ibm.com>,
        Julian Ruess <julianr@linux.ibm.com>,
        Pierre Morel <pmorel@linux.ibm.com>,
        Alexandra Winter <wintera@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Sven Schnelle <svens@linux.ibm.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
        Hector Martin <marcan@marcan.st>,
        Sven Peter <sven@svenpeter.dev>,
        Alyssa Rosenzweig <alyssa@rosenzweig.io>,
        David Woodhouse <dwmw2@infradead.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Yong Wu <yong.wu@mediatek.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
        Orson Zhai <orsonzhai@gmail.com>,
        Baolin Wang <baolin.wang@linux.alibaba.com>,
        Chunyan Zhang <zhang.lyra@gmail.com>,
        Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Samuel Holland <samuel@sholland.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        Krishna Reddy <vdumpa@nvidia.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Jonathan Corbet <corbet@lwn.net>, linux-s390@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        iommu@lists.linux.dev, asahi@lists.linux.dev,
        linux-arm-kernel@lists.infradead.org,
        linux-arm-msm@vger.kernel.org, linux-mediatek@lists.infradead.org,
        linux-sunxi@lists.linux.dev, linux-tegra@vger.kernel.org,
        linux-doc@vger.kernel.org
References: <20230310-dma_iommu-v9-0-65bb8edd2beb@linux.ibm.com>
 <20230310-dma_iommu-v9-5-65bb8edd2beb@linux.ibm.com>
 <b1e53f39-5e0b-a09d-2954-cdc9e8592b67@arm.com>
 <0d9e3f86cf9a1a3d69e650fb631809498c2cd01e.camel@linux.ibm.com>
From:   Robin Murphy <robin.murphy@arm.com>
In-Reply-To: <0d9e3f86cf9a1a3d69e650fb631809498c2cd01e.camel@linux.ibm.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 2023-05-23 13:02, Niklas Schnelle wrote:
[...]
>>> +static void fq_flush_single(struct iommu_dma_cookie *cookie)
>>> +{
>>> +	struct iova_fq *fq = cookie->single_fq;
>>> +	unsigned long flags;
>>> +
>>> +	spin_lock_irqsave(&fq->lock, flags);
>>> +	fq_ring_free(cookie, fq);
>>> +	spin_unlock_irqrestore(&fq->lock, flags)
>>
>> Nit: this should clearly just be a self-locked version of fq_ring_free()
>> that takes fq as an argument, then both the new case and the existing
>> loop body become trivial one-line calls.
> 
> Sure will do. Just one question about names. As an example
> pci_reset_function_locked() means that the relevant lock is already
> taken with pci_reset_function() adding the lock/unlock. In your wording
> the implied function names sound the other way around. I can't find
> anything similar in drivers/iommu so would you mind going the PCI way
> and having:
> 
> fq_ring_free_locked(): Called in queue_iova() with the lock held
> fr_ring_free(): Called in fq_flush_timeout() takes the lock itself
> 
> Or maybe I'm just biased because I've used the PCI ..locked() functions
> before and there is a better convention.

Yes, that's the form that's most familiar to me too - sorry I failed to 
express it clearly :)

Thanks,
Robin.