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

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Message-ID: <20231204183603.GN1493156@nvidia.com>
Date:   Mon, 4 Dec 2023 14:36:03 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Yan Zhao <yan.y.zhao@...el.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 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

Jason