linux-kernel - Re: [PATCH v7 08/11] vfio: Remove use of vfio_group

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Date:   Mon, 28 Feb 2022 15:06:21 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joerg Roedel <joro@...tes.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Dan Williams <dan.j.williams@...el.com>, rafael@...nel.org,
        Diana Craciun <diana.craciun@....nxp.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Chaitanya Kulkarni <kch@...dia.com>,
        Stuart Yoder <stuyoder@...il.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Li Yang <leoyang.li@....com>,
        Dmitry Osipenko <digetx@...il.com>,
        iommu@...ts.linux-foundation.org, linux-pci@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 08/11] vfio: Remove use of vfio_group_viable()

On Mon, 28 Feb 2022 08:50:53 +0800
Lu Baolu <baolu.lu@...ux.intel.com> wrote:

> As DMA ownership is claimed for the iommu group when a VFIO group is
> added to a VFIO container, the VFIO group viability is guaranteed as long
> as group->container_users > 0. Remove those unnecessary group viability
> checks which are only hit when group->container_users is not zero.
> 
> The only remaining reference is in GROUP_GET_STATUS, which could be called
> at any time when group fd is valid. Here we just replace the
> vfio_group_viable() by directly calling IOMMU core to get viability status.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
> ---
>  drivers/vfio/vfio.c | 18 ++++++------------
>  1 file changed, 6 insertions(+), 12 deletions(-)

Acked-by: Alex Williamson <alex.williamson@...hat.com>