linux-kernel - Re: [PATCH 0/2] Introduce PCI_FIXUP

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Date:   Tue, 23 Jun 2020 15:48:25 +0800
From:   Zhangfei Gao <zhangfei.gao@...aro.org>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Sudeep Holla <sudeep.holla@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        jean-philippe <jean-philippe@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        kenneth-lee-2012@...mail.com, Wangzhou <wangzhou1@...ilicon.com>,
        linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-acpi@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 0/2] Introduce PCI_FIXUP_IOMMU

Hi, Joerg

On 2020/6/22 下午7:55, Joerg Roedel wrote:
> On Thu, Jun 04, 2020 at 09:33:07PM +0800, Zhangfei Gao wrote:
>> +++ b/drivers/iommu/iommu.c
>> @@ -2418,6 +2418,10 @@ int iommu_fwspec_init(struct device *dev, struct
>> fwnode_handle *iommu_fwnode,
>>          fwspec->iommu_fwnode = iommu_fwnode;
>>          fwspec->ops = ops;
>>          dev_iommu_fwspec_set(dev, fwspec);
>> +
>> +       if (dev_is_pci(dev))
>> +               pci_fixup_device(pci_fixup_final, to_pci_dev(dev));
>> +
> That's not going to fly, I don't think we should run the fixups twice,
> and they should not be run from IOMMU code. Is the only reason for this
> second pass that iommu_fwspec is not yet allocated when it runs the
> first time? I ask because it might be easier to just allocate the struct
> earlier then.
Thanks for looking this.

Yes, it is the only reason calling fixup secondly after iommu_fwspec is 
allocated.

The first time fixup final is very early in pci_bus_add_device.
If allocating iommu_fwspec earlier, it maybe in pci_alloc_dev.
And assigning ops still in iommu_fwspec_init.
Have tested it works.
Not sure is it acceptable?

Alternatively, adding can_stall to struct pci_dev is simple but ugly too,
since pci does not know stall now.


Thanks