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From: Jiang Liu <jiang.liu@linux.intel.com>
To: Marc Zyngier <marc.zyngier@arm.com>,
	Yijing Wang <wangyijing@huawei.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Thomas Gleixner <tglx@linutronix.de>
Cc: "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Will Deacon <Will.Deacon@arm.com>,
	"suravee.suthikulpanit@amd.com" <suravee.suthikulpanit@amd.com>
Subject: Re: [PATCH 2/6] PCI/MSI: add hooks to populate the msi_domain field
Date: Tue, 09 Dec 2014 22:11:14 +0800	[thread overview]
Message-ID: <54870302.5050703@linux.intel.com> (raw)
In-Reply-To: <5487012B.4040505@arm.com>

On 2014/12/9 22:03, Marc Zyngier wrote:
> Hi Gerry,
> 
> On 09/12/14 12:47, Jiang Liu wrote:
>> On 2014/12/9 20:12, Marc Zyngier wrote:
>>> Yijing,
>>>
>>> On 09/12/14 11:57, Yijing Wang wrote:
>>>>>>> +void __weak pcibios_set_phb_msi_domain(struct pci_bus *bus)
>>>>>>> +{
>>>>>>> +}
>>>>>>> +
>>>>>>> +static void pci_set_bus_msi_domain(struct pci_bus *bus)
>>>>>>> +{
>>>>>>> +	struct pci_dev *bridge = bus->self;
>>>>>>> +
>>>>>>> +	if (!bridge)
>>>>>>> +		pcibios_set_phb_msi_domain(bus);
>>>>>>> +	else
>>>>>>> +		dev_set_msi_domain(&bus->dev, dev_get_msi_domain(&bridge->dev));
>>>>>>> +}
>>>>>>
>>>>>>
>>>>>> Hi Marc, we can not assume pci devices under same phb share the same msi irq domain,
>>>>>> now in x86, pci devices under the same phb may associate different msi irq domain.
>>>>
>>>> Hi Marc,
>>>>
>>>>>
>>>>> Well, this is not supposed to be a perfect solution yet, but instead a
>>>>> basis for discussion. What I'd like to find out is:
>>>>>
>>>>> - What is the minimum granularity for associating a device with its MSI
>>>>> domain in existing platforms?
>>>>
>>>> PCI device, after Gerry's msi irq domain patchset which now in linux-next,
>>>> in x86, we will find msi irq domain by pci_dev.
>>>
>>> Are you *really* associating the MSI domain on a per pci-device basis?
>>> That is, you have devices on the same PCI bus talking to different MSI hw?
>> Hi Marc,
>> 	This is a little wild:(
>> 	On x86 platform with Intel VT-d(not the case for AMD-v),
>> interrupt remapping is tight to DMA remapping (IOMMU) unit.
>> For most common cases, IOMMU unit manages PCI bus and its sub-hierarchy.
>> But it may also manage a specific PCI device. This is typically used to
>> provide QoS for audio device by using dedicated IOMMU unit to avoid
>> resource contention on DMA remapping tables. BIOS uses ACPI table to
>> report PCI bus/device to IOMMU unit mapping relationship. (To be honest,
>> I have no really experience with such a hardware platform yet, just for
>> theoretical analysis)
>> 	On the other hand, we now support hierarchy irqdomain. So to
>> support per-PCI IOMMU unit case, we need maintain irqdomain at PCI
>> device level.
>> 	This piece of code from your [4/6] is flexible enough, which
>> retrieves msi_domain from PCI device, then fallback to PCI bus,
>> then fallback to platform specific method.
>> 	domain = dev_get_msi_domain(&dev->dev);
>> 	if (!domain && dev->bus->msi)
>>  		domain = dev->bus->msi->domain;
>>  	if (!domain)
>>  		domain = arch_get_pci_msi_domain(dev);
> 
> OK. But what I'd really like to see is a way to setup the
> device<->domain binding as early as possible, without having to use more
> conditional code in pci_msi_get_domain.
> 
> IOW, can we do something similar to what pci_set_bus_msi_domain and
> pci_set_msi_domain do in this patch?
Hi Marc,
	I have checked x86 code, we could set pci_dev->msi_domain
when creating PCI devices, just need to find some hook points
into PCI core next step. If arch code doesn't set pci_dev->msi_domain,
PCI MSI core may provide a default way to set pci_dev->msi_domain.
This may make the implementation simpler, I guess:)
Thanks!
Gerry

> 
> Thanks,
> 
> 	M.
> 

  reply	other threads:[~2014-12-09 14:13 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-08 20:12 [PATCH 0/6] Introducing per-device MSI domain Marc Zyngier
2014-12-08 20:12 ` [PATCH 1/6] device core: Introduce per-device MSI domain pointer Marc Zyngier
2014-12-08 20:12 ` [PATCH 2/6] PCI/MSI: add hooks to populate the msi_domain field Marc Zyngier
2014-12-09  2:03   ` Yijing Wang
2014-12-09 10:02     ` Marc Zyngier
2014-12-09 11:57       ` Yijing Wang
2014-12-09 12:12         ` Marc Zyngier
2014-12-09 12:24           ` Yijing Wang
2014-12-09 12:47           ` Jiang Liu
2014-12-09 14:03             ` Marc Zyngier
2014-12-09 14:11               ` Jiang Liu [this message]
2014-12-09 14:27                 ` Marc Zyngier
2014-12-09 14:35                   ` Jiang Liu
2014-12-09 14:59                     ` Marc Zyngier
2014-12-09 15:42                       ` Jiang Liu
2014-12-09 12:57   ` Jiang Liu
2015-01-27  0:40   ` Bjorn Helgaas
2015-01-27  0:43     ` Bjorn Helgaas
2014-12-08 20:12 ` [PATCH 3/6] PCI/MSI: of: add support for OF-provided msi_domain Marc Zyngier
2015-01-27  0:41   ` Bjorn Helgaas
2014-12-08 20:12 ` [PATCH 4/6] PCI/MSI: Let pci_msi_get_domain use struct device's msi_domain Marc Zyngier
2014-12-08 20:12 ` [PATCH 5/6] irqchip: GICv2m: Get rid of struct msi_controller Marc Zyngier
2014-12-08 20:12 ` [PATCH 6/6] irqchip: gicv3-its: " Marc Zyngier

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