linux-kernel - Re: [RFC PATCH 16/42] iommufd: Enable device feature IOPF during device attachment to KVM HWPT

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Message-ID: <ZW7NwSCzswweHZh6@yzhao56-desk.sh.intel.com>
Date:   Tue, 5 Dec 2023 15:14:09 +0800
From:   Yan Zhao <yan.y.zhao@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     <iommu@...ts.linux.dev>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <alex.williamson@...hat.com>,
        <pbonzini@...hat.com>, <seanjc@...gle.com>, <joro@...tes.org>,
        <will@...nel.org>, <robin.murphy@....com>, <kevin.tian@...el.com>,
        <baolu.lu@...ux.intel.com>, <dwmw2@...radead.org>,
        <yi.l.liu@...el.com>
Subject: Re: [RFC PATCH 16/42] iommufd: Enable device feature IOPF during
 device attachment to KVM HWPT

On Mon, Dec 04, 2023 at 02:36:03PM -0400, Jason Gunthorpe wrote:
> On Sat, Dec 02, 2023 at 05:23:11PM +0800, Yan Zhao wrote:
> > Enable device feature IOPF during device attachment to KVM HWPT and abort
> > the attachment if feature enabling is failed.
> > 
> > "pin" is not done by KVM HWPT. If VMM wants to create KVM HWPT, it must
> > know that all devices attached to this HWPT support IOPF so that pin-all
> > is skipped.
> > 
> > Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
> > ---
> >  drivers/iommu/iommufd/device.c | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> > 
> > diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> > index 83af6b7e2784b..4ea447e052ce1 100644
> > --- a/drivers/iommu/iommufd/device.c
> > +++ b/drivers/iommu/iommufd/device.c
> > @@ -381,10 +381,26 @@ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
> >  			goto err_unresv;
> >  		idev->igroup->hwpt = hwpt;
> >  	}
> > +	if (hwpt_is_kvm(hwpt)) {
> > +		/*
> > +		 * Feature IOPF requires ats is enabled which is true only
> > +		 * after device is attached to iommu domain.
> > +		 * So enable dev feature IOPF after iommu_attach_group().
> > +		 * -EBUSY will be returned if feature IOPF is already on.
> > +		 */
> > +		rc = iommu_dev_enable_feature(idev->dev, IOMMU_DEV_FEAT_IOPF);
> > +		if (rc && rc != -EBUSY)
> > +			goto err_detach;
> 
> I would like to remove IOMMU_DEV_FEAT_IOPF completely please

So, turn on device PRI during device attachment in IOMMU vendor driver?