From: "Chen, Jiqian" <Jiqian.Chen@amd.com>
To: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: "Rafael J . Wysocki" <rafael@kernel.org>,
Len Brown <lenb@kernel.org>, Bjorn Helgaas <bhelgaas@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
"Deucher, Alexander" <Alexander.Deucher@amd.com>,
"Koenig, Christian" <Christian.Koenig@amd.com>,
"Huang, Ray" <Ray.Huang@amd.com>,
"Chen, Jiqian" <Jiqian.Chen@amd.com>
Subject: Re: [RFC KERNEL PATCH v3 3/3] PCI/sysfs: Add gsi sysfs for pci_dev
Date: Thu, 14 Dec 2023 07:08:32 +0000 [thread overview]
Message-ID: <BL1PR12MB584911B4DFF4D9ED65CF92F0E78CA@BL1PR12MB5849.namprd12.prod.outlook.com> (raw)
In-Reply-To: <ZXmfmbb4S8Iuy7si@macbook>
On 2023/12/13 20:12, Roger Pau Monné wrote:
> On Wed, Dec 13, 2023 at 03:31:21AM +0000, Chen, Jiqian wrote:
>> On 2023/12/12 17:18, Roger Pau Monné wrote:
>>> On Tue, Dec 12, 2023 at 06:34:27AM +0000, Chen, Jiqian wrote:
>>>>
>>>> On 2023/12/12 01:57, Roger Pau Monné wrote:
>>>>> On Mon, Dec 11, 2023 at 12:15:19AM +0800, Jiqian Chen wrote:
>>>>>> There is a need for some scenarios to use gsi sysfs.
>>>>>> For example, when xen passthrough a device to dumU, it will
>>>>>> use gsi to map pirq, but currently userspace can't get gsi
>>>>>> number.
>>>>>> So, add gsi sysfs for that and for other potential scenarios.
>>>>>>
>>>>>> Co-developed-by: Huang Rui <ray.huang@amd.com>
>>>>>> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
>>>>>> ---
>>>>>> drivers/acpi/pci_irq.c | 1 +
>>>>>> drivers/pci/pci-sysfs.c | 11 +++++++++++
>>>>>> include/linux/pci.h | 2 ++
>>>>>> 3 files changed, 14 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c
>>>>>> index 630fe0a34bc6..739a58755df2 100644
>>>>>> --- a/drivers/acpi/pci_irq.c
>>>>>> +++ b/drivers/acpi/pci_irq.c
>>>>>> @@ -449,6 +449,7 @@ int acpi_pci_irq_enable(struct pci_dev *dev)
>>>>>> kfree(entry);
>>>>>> return 0;
>>>>>> }
>>>>>> + dev->gsi = gsi;
>>>>>
>>>>> It would be better if the gsi if fetched without requiring calling
>>>>> acpi_pci_irq_enable(), as the gsi doesn't require the interrupt to be
>>>>> enabled. The gsi is known at boot time and won't change for the
>>>>> lifetime of the device.
>>>> Do you have any suggest places to do this?
>>>
>>> I'm not an expert on this, but drivers/pci/pci-sysfs.c would seem like
>>> a better place, together with the rest of the resources.
>> I'm not familiar with this too. But it seems pci-sysfs.c only creates sysfs node and supports the read/write method without initializing the values.
>> If want to initialize the value of gsi here. An approach to initialize it is to call acpi_pci_irq_lookup to get gsi number when the first time it is read?
>
> Hm, maybe, I don't really have much experience with sysfs, so don't
> know how nodes are usually initialized.
Maybe the maintainers of sysfs can give some suggest places to initialize the value of gsi.
>
>>>
>>> Maybe my understanding is incorrect, but given the suggested placement
>>> in acpi_pci_irq_enable() I think the device would need to bind the
>>> interrupt in order for the gsi node to appear on sysfs?
>> No, gsi sysfs has existed there, in acpi_pci_irq_enable is to initialize the value of gsi.
>>
>>>
>>> Would the current approach work if the device is assigned to pciback
>>> on the kernel command line, and thus never owned by any driver in
>>> dom0?
>> If assigned to pciback, I think pciback will enable the device, and then acpi_pci_irq_enable will be called, and then the gsi will be initialized. So, current can work.
>
> This needs checking to be sure, I'm certainly not that familiar. You
> would need to at least test that it works properly when the device is
> hidden using xen-pciback.hide=(SBDF) in the Linux kernel command line.
Sure, I have validated it on my side. Both the "Static assignment for built-in xen-pciback(xen-pciback.hide=(SBDF))" and the "Dynamic assignment with xl(sudo modprobe xen-pciback & sudo xl pci-assignable-add SBDF)" can work fine with current implementation.
>
> Thanks, Roger.
--
Best regards,
Jiqian Chen.
next prev parent reply other threads:[~2023-12-14 7:08 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-10 16:15 [RFC KERNEL PATCH v3 0/3] Support device passthrough when dom0 is PVH on Xen Jiqian Chen
2023-12-10 16:15 ` [RFC KERNEL PATCH v3 1/3] xen/pci: Add xen_reset_device_state function Jiqian Chen
2023-12-12 8:08 ` Roger Pau Monné
2023-12-13 3:02 ` Chen, Jiqian
2023-12-10 16:15 ` [RFC KERNEL PATCH v3 2/3] xen/pvh: Setup gsi and map pirq for passthrough device Jiqian Chen
2023-12-10 16:15 ` [RFC KERNEL PATCH v3 3/3] PCI/sysfs: Add gsi sysfs for pci_dev Jiqian Chen
2023-12-11 17:57 ` Roger Pau Monné
2023-12-12 6:34 ` Chen, Jiqian
2023-12-12 9:18 ` Roger Pau Monné
2023-12-13 3:31 ` Chen, Jiqian
2023-12-13 12:12 ` Roger Pau Monné
2023-12-14 7:08 ` Chen, Jiqian [this message]
2023-12-14 8:46 ` Roger Pau Monné
2023-12-14 9:03 ` Chen, Jiqian
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