linux-kernel - Re: [PATCH] vfio/pci: update igd matching conditions

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Message-ID: <85002952-bae6-4e35-9af7-db28a593d458@gmail.com>
Date: Mon, 30 Dec 2024 01:04:13 +0800
From: Tomita Moeko <tomitamoeko@...il.com>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vfio/pci: update igd matching conditions

On 12/30/24 00:26, Alex Williamson wrote:
> On Sun, 29 Dec 2024 23:51:40 +0800
> Tomita Moeko <tomitamoeko@...il.com> wrote:
> 
>> igd device can either expose as a VGA controller or display controller
>> depending on whether it is configured as the primary display device in
>> BIOS. In both cases, the OpRegion may be present. Also checks if the
>> device is at bdf 00:02.0 to avoid setting up igd-specific regions on
>> Intel discrete GPUs.
>>
>> Signed-off-by: Tomita Moeko <tomitamoeko@...il.com>
>> ---
>>  drivers/vfio/pci/vfio_pci.c | 6 ++++--
>>  1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
>> index e727941f589d..051ef4ad3f43 100644
>> --- a/drivers/vfio/pci/vfio_pci.c
>> +++ b/drivers/vfio/pci/vfio_pci.c
>> @@ -111,9 +111,11 @@ static int vfio_pci_open_device(struct vfio_device *core_vdev)
>>  	if (ret)
>>  		return ret;
>>  
>> -	if (vfio_pci_is_vga(pdev) &&
>> +	if (IS_ENABLED(CONFIG_VFIO_PCI_IGD) &&
>>  	    pdev->vendor == PCI_VENDOR_ID_INTEL &&
>> -	    IS_ENABLED(CONFIG_VFIO_PCI_IGD)) {
>> +	    ((pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA ||
> 
> The above is vfio_pci_is_vga(pdev), maybe below should have a similar
> helper.

There isn't, shall I create a new helper function? or just keep it as
the match only happens here.
 
>> +	     (pdev->class >> 8) == PCI_CLASS_DISPLAY_OTHER) &&
>> +	    pdev == pci_get_domain_bus_and_slot(0, 0, PCI_DEVFN(2, 0))) {
> 
> This increments the reference count on the device:
> 
>  * Given a PCI domain, bus, and slot/function number, the desired PCI
>  * device is located in the list of PCI devices. If the device is
>  * found, its reference count is increased and this function returns a
>  * pointer to its data structure.  The caller must decrement the
>  * reference count by calling pci_dev_put().

Sorry I missed that, will fix in v2.

>>  		ret = vfio_pci_igd_init(vdev);
>>  		if (ret && ret != -ENODEV) {
>>  			pci_warn(pdev, "Failed to setup Intel IGD regions\n");
>