linux-kernel - Re: [PATCH v2 10/10] vfio: Do not allow !ops->dma_unmap in vfio_pin/unpin

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Date:   Thu, 9 Feb 2023 09:26:15 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>
Cc:     Nicolin Chen <nicolinc@...dia.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "will@...nel.org" <will@...nel.org>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "shuah@...nel.org" <shuah@...nel.org>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>
Subject: Re: [PATCH v2 10/10] vfio: Do not allow !ops->dma_unmap in
 vfio_pin/unpin_pages()

On Thu, Feb 09, 2023 at 04:10:04AM +0000, Tian, Kevin wrote:
> > From: Nicolin Chen <nicolinc@...dia.com>
> > Sent: Wednesday, February 8, 2023 5:18 AM
> > 
> > A driver that doesn't implement ops->dma_unmap shouldn't be allowed to
> > do
> > vfio_pin/unpin_pages(), though it can use vfio_dma_rw() to access an iova
> > range. Deny !ops->dma_unmap cases in vfio_pin/unpin_pages().
> > 
> > Suggested-by: Kevin Tian <kevin.tian@...el.com>
> > Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> > ---
> >  drivers/vfio/vfio_main.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c
> > index 8559c3dfb335..c7f3251ad6e5 100644
> > --- a/drivers/vfio/vfio_main.c
> > +++ b/drivers/vfio/vfio_main.c
> > @@ -1543,6 +1543,8 @@ int vfio_pin_pages(struct vfio_device *device,
> > dma_addr_t iova,
> > 
> >  		if (iova > ULONG_MAX)
> >  			return -EINVAL;
> > +		if (!device->ops->dma_unmap)
> > +			return -EINVAL;
> >  		/*
> >  		 * VFIO ignores the sub page offset, npages is from the start
> > of
> >  		 * a PAGE_SIZE chunk of IOVA. The caller is expected to
> > recover
> > @@ -1580,6 +1582,8 @@ void vfio_unpin_pages(struct vfio_device *device,
> > dma_addr_t iova, int npage)
> >  	if (device->iommufd_access) {
> >  		if (WARN_ON(iova > ULONG_MAX))
> >  			return;
> > +		if (!device->ops->dma_unmap)
> > +			return;
> 
> IMHO this restriction applies to both iommufd and legacy container.

Yeah that makes sense

Jason