linux-kernel - Re: [PATCH v3 6/7] vfio: Wait for dma-buf invalidation to complete

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <107464758df9444a465a3a9e387f5a42827aff51.camel@linux.intel.com>
Date: Wed, 21 Jan 2026 10:36:09 +0100
From: Thomas Hellström <thomas.hellstrom@...ux.intel.com>
To: Christian König <christian.koenig@....com>, Leon
 Romanovsky <leon@...nel.org>, Sumit Semwal <sumit.semwal@...aro.org>, Alex
 Deucher	 <alexander.deucher@....com>, David Airlie <airlied@...il.com>,
 Simona Vetter	 <simona@...ll.ch>, Gerd Hoffmann <kraxel@...hat.com>, Dmitry
 Osipenko	 <dmitry.osipenko@...labora.com>, Gurchetan Singh
 <gurchetansingh@...omium.org>,  Chia-I Wu <olvaffe@...il.com>, Maarten
 Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard	
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, Lucas De
 Marchi	 <lucas.demarchi@...el.com>, Rodrigo Vivi <rodrigo.vivi@...el.com>,
 Jason Gunthorpe <jgg@...pe.ca>, Kevin Tian <kevin.tian@...el.com>, Joerg
 Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>, Robin Murphy
 <robin.murphy@....com>, Felix Kuehling	 <Felix.Kuehling@....com>, Alex
 Williamson <alex@...zbot.org>, Ankit Agrawal	 <ankita@...dia.com>, Vivek
 Kasireddy <vivek.kasireddy@...el.com>
Cc: linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org, 
	amd-gfx@...ts.freedesktop.org, virtualization@...ts.linux.dev, 
	intel-xe@...ts.freedesktop.org, linux-rdma@...r.kernel.org, 
	iommu@...ts.linux.dev, kvm@...r.kernel.org
Subject: Re: [PATCH v3 6/7] vfio: Wait for dma-buf invalidation to complete

Hi, Christian,

On Wed, 2026-01-21 at 10:20 +0100, Christian König wrote:
> On 1/20/26 15:07, Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@...dia.com>
> > 
> > dma-buf invalidation is performed asynchronously by hardware, so
> > VFIO must
> > wait until all affected objects have been fully invalidated.
> > 
> > Fixes: 5d74781ebc86 ("vfio/pci: Add dma-buf export support for MMIO
> > regions")
> > Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> 
> Reviewed-by: Christian König <christian.koenig@....com>
> 
> Please also keep in mind that the while this wait for all fences for
> correctness you also need to keep the mapping valid until
> dma_buf_unmap_attachment() was called.

I'm wondering shouldn't we require DMA_RESV_USAGE_BOOKKEEP here, as
*any* unsignaled fence could indicate access through the map?

/Thomas

> 
> In other words you can only redirect the DMA-addresses previously
> given out into nirvana (or a dummy memory or similar), but you still
> need to avoid re-using them for something else.
> 
> Regards,
> Christian.
> 
> > ---
> >  drivers/vfio/pci/vfio_pci_dmabuf.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c
> > b/drivers/vfio/pci/vfio_pci_dmabuf.c
> > index d4d0f7d08c53..33bc6a1909dd 100644
> > --- a/drivers/vfio/pci/vfio_pci_dmabuf.c
> > +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c
> > @@ -321,6 +321,9 @@ void vfio_pci_dma_buf_move(struct
> > vfio_pci_core_device *vdev, bool revoked)
> >  			dma_resv_lock(priv->dmabuf->resv, NULL);
> >  			priv->revoked = revoked;
> >  			dma_buf_move_notify(priv->dmabuf);
> > +			dma_resv_wait_timeout(priv->dmabuf->resv,
> > +					     
> > DMA_RESV_USAGE_KERNEL, false,
> > +					     
> > MAX_SCHEDULE_TIMEOUT);
> >  			dma_resv_unlock(priv->dmabuf->resv);
> >  		}
> >  		fput(priv->dmabuf->file);
> > @@ -342,6 +345,8 @@ void vfio_pci_dma_buf_cleanup(struct
> > vfio_pci_core_device *vdev)
> >  		priv->vdev = NULL;
> >  		priv->revoked = true;
> >  		dma_buf_move_notify(priv->dmabuf);
> > +		dma_resv_wait_timeout(priv->dmabuf->resv,
> > DMA_RESV_USAGE_KERNEL,
> > +				      false,
> > MAX_SCHEDULE_TIMEOUT);
> >  		dma_resv_unlock(priv->dmabuf->resv);
> >  		vfio_device_put_registration(&vdev->vdev);
> >  		fput(priv->dmabuf->file);
> >