Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Message-ID: <d928d256-b1bc-2d45-a9c3-382edfe67b80@linux.intel.com>
Date:   Tue, 19 Apr 2022 07:37:57 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101
 Thunderbird/91.8.0
Cc:     baolu.lu@linux.intel.com, iommu@lists.linux-foundation.org,
        sven@svenpeter.dev, robdclark@gmail.com, m.szyprowski@samsung.com,
        yong.wu@mediatek.com, mjrosato@linux.ibm.com,
        gerald.schaefer@linux.ibm.com, zhang.lyra@gmail.com,
        thierry.reding@gmail.com, vdumpa@nvidia.com,
        jean-philippe@linaro.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
Content-Language: en-US
To:     Robin Murphy <robin.murphy@arm.com>, joro@8bytes.org,
        will@kernel.org
References: <cover.1649935679.git.robin.murphy@arm.com>
 <e607a32be8e84c56d65160902f4bd3fb434ee9d3.1649935679.git.robin.murphy@arm.com>
 <d838c7f8-2d31-2327-9b4d-c05b06a516bb@linux.intel.com>
 <1d9a2146-9e48-ba97-d049-5d2332ebbd3a@arm.com>
From:   Lu Baolu <baolu.lu@linux.intel.com>
Subject: Re: [PATCH 02/13] iommu: Move bus setup to IOMMU device registration
In-Reply-To: <1d9a2146-9e48-ba97-d049-5d2332ebbd3a@arm.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 2022/4/19 6:09, Robin Murphy wrote:
> On 2022-04-16 01:04, Lu Baolu wrote:
>> On 2022/4/14 20:42, Robin Murphy wrote:
>>> @@ -1883,27 +1900,12 @@ static int iommu_bus_init(struct bus_type *bus)
>>>    */
>>>   int bus_set_iommu(struct bus_type *bus, const struct iommu_ops *ops)
>>>   {
>>> -    int err;
>>> -
>>> -    if (ops == NULL) {
>>> -        bus->iommu_ops = NULL;
>>> -        return 0;
>>> -    }
>>> -
>>> -    if (bus->iommu_ops != NULL)
>>> +    if (bus->iommu_ops && ops && bus->iommu_ops != ops)
>>>           return -EBUSY;
>>>       bus->iommu_ops = ops;
>>
>> Do we still need to keep above lines in bus_set_iommu()?
> 
> It preserves the existing behaviour until each callsite and its 
> associated error handling are removed later on, which seems like as good 
> a thing to do as any. Since I'm already relaxing iommu_device_register() 
> to a warn-but-continue behaviour while it keeps the bus ops on 
> life-support internally, I figured not changing too much at once would 
> make it easier to bisect any potential issues arising from this first step.

Fair enough. Thank you for the explanation.

Do you have a public tree that I could pull these patches and try them
on an Intel hardware? Or perhaps you have done this? I like the whole
idea of this series, but it's better to try it with a real hardware.

Best regards,
baolu