linux-kernel - Re: [PATCH v6 05/20] vfio: mdev: common lib code for setting up Interrupt Message Store

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Date:   Fri, 28 May 2021 09:37:56 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     alex.williamson@...hat.com, kwankhede@...dia.com,
        tglx@...utronix.de, vkoul@...nel.org, megha.dey@...el.com,
        jacob.jun.pan@...el.com, ashok.raj@...el.com, yi.l.liu@...el.com,
        baolu.lu@...el.com, kevin.tian@...el.com, sanjay.k.kumar@...el.com,
        tony.luck@...el.com, dan.j.williams@...el.com,
        eric.auger@...hat.com, pbonzini@...hat.com,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH v6 05/20] vfio: mdev: common lib code for setting up
 Interrupt Message Store


On 5/28/2021 5:21 AM, Jason Gunthorpe wrote:
> On Thu, May 27, 2021 at 06:49:59PM -0700, Dave Jiang wrote:
>>>> +static int mdev_msix_enable(struct mdev_irq *mdev_irq, int nvec)
>>>> +{
>>>> +	struct mdev_device *mdev = irq_to_mdev(mdev_irq);
>>>> +	struct device *dev;
>>>> +	int rc;
>>>> +
>>>> +	if (nvec != mdev_irq->num)
>>>> +		return -EINVAL;
>>>> +
>>>> +	if (mdev_irq->ims_num) {
>>>> +		dev = &mdev->dev;
>>>> +		rc = msi_domain_alloc_irqs(dev_get_msi_domain(dev), dev, mdev_irq->ims_num);
>>> Huh? The PCI device should be the only device touching IRQ stuff. I'm
>>> nervous to see you mix in the mdev struct device into this function.
>> As we talked about in the other thread. We have a single IMS domain per
>> device. The domain is set to the mdev 'struct device' and we allocate the
>> vectors to each mdev 'struct device' so we can manage those IMS vectors
>> specifically for that mdev.
> That is not the point, I'm asking if you should be calling
> dev_set_msi_domain(mdev) at all

I'm not familiar with the standard way of doing this. Should I not set 
the domain to the mdev 'struct device' because I can have multiple mdev 
using the same domain? With the domain set, I am able to retrieve it and 
call the msi_domain_alloc_irqs() in common code. Alternatively we can 
pass in the domain during init and not rely on dev->msi_domain.


>
> Jason