linux-kernel - Re: [PATCH v7 05/11] PCI: pci_stub: Set driver_managed_dma

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Message-ID: <20220228195418.GA515725@bhelgaas>
Date:   Mon, 28 Feb 2022 13:54:18 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        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>, kvm@...r.kernel.org,
        rafael@...nel.org, David Airlie <airlied@...ux.ie>,
        linux-pci@...r.kernel.org,
        Thierry Reding <thierry.reding@...il.com>,
        Diana Craciun <diana.craciun@....nxp.com>,
        Dmitry Osipenko <digetx@...il.com>,
        Will Deacon <will@...nel.org>,
        Stuart Yoder <stuyoder@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Chaitanya Kulkarni <kch@...dia.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Cornelia Huck <cohuck@...hat.com>,
        linux-kernel@...r.kernel.org, Li Yang <leoyang.li@....com>,
        iommu@...ts.linux-foundation.org,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH v7 05/11] PCI: pci_stub: Set driver_managed_dma

On Mon, Feb 28, 2022 at 08:50:50AM +0800, Lu Baolu wrote:
> The current VFIO implementation allows pci-stub driver to be bound to
> a PCI device with other devices in the same IOMMU group being assigned
> to userspace. The pci-stub driver has no dependencies on DMA or the
> IOVA mapping of the device, but it does prevent the user from having
> direct access to the device, which is useful in some circumstances.
> 
> The pci_dma_configure() marks the iommu_group as containing only devices
> with kernel drivers that manage DMA. For compatibility with the VFIO
> usage, avoid this default behavior for the pci_stub. This allows the
> pci_stub still able to be used by the admin to block driver binding after
> applying the DMA ownership to VFIO.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

> ---
>  drivers/pci/pci-stub.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/pci/pci-stub.c b/drivers/pci/pci-stub.c
> index e408099fea52..d1f4c1ce7bd1 100644
> --- a/drivers/pci/pci-stub.c
> +++ b/drivers/pci/pci-stub.c
> @@ -36,6 +36,7 @@ static struct pci_driver stub_driver = {
>  	.name		= "pci-stub",
>  	.id_table	= NULL,	/* only dynamic id's */
>  	.probe		= pci_stub_probe,
> +	.driver_managed_dma = true,
>  };
>  
>  static int __init pci_stub_init(void)
> -- 
> 2.25.1
> 
> _______________________________________________
> iommu mailing list
> iommu@...ts.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu

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