linux-kernel - Re: [PATCH v9 10/11] vfio/pci: Add dma-buf export support for MMIO regions

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Message-ID: <20251121002344.GC233636@ziepe.ca>
Date: Thu, 20 Nov 2025 20:23:44 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Alex Williamson <alex@...zbot.org>
Cc: Leon Romanovsky <leon@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Logan Gunthorpe <logang@...tatee.com>, Jens Axboe <axboe@...nel.dk>,
	Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Christian König <christian.koenig@....com>,
	Kees Cook <kees@...nel.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Ankit Agrawal <ankita@...dia.com>,
	Yishai Hadas <yishaih@...dia.com>,
	Shameer Kolothum <skolothumtho@...dia.com>,
	Kevin Tian <kevin.tian@...el.com>,
	Krishnakant Jaju <kjaju@...dia.com>, Matt Ochs <mochs@...dia.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org, iommu@...ts.linux.dev,
	linux-mm@...ck.org, linux-doc@...r.kernel.org,
	linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linaro-mm-sig@...ts.linaro.org, kvm@...r.kernel.org,
	linux-hardening@...r.kernel.org,
	Vivek Kasireddy <vivek.kasireddy@...el.com>
Subject: Re: [PATCH v9 10/11] vfio/pci: Add dma-buf export support for MMIO
 regions

On Thu, Nov 20, 2025 at 05:04:13PM -0700, Alex Williamson wrote:

> @@ -2501,7 +2501,7 @@ static int vfio_pci_dev_set_hot_reset(struct vfio_device_set *dev_set,
>  err_undo:
>         list_for_each_entry_from_reverse(vdev, &dev_set->device_list,
>                                          vdev.dev_set_list) {
> -               if (__vfio_pci_memory_enabled(vdev))
> +               if (vdev->vdev.open_count && __vfio_pci_memory_enabled(vdev))
>                         vfio_pci_dma_buf_move(vdev, false);
>                 up_write(&vdev->memory_lock);
>         }
> 
> Any other suggestions?  This should be the only reset path with this
> nuance of affecting non-opened devices.  Thanks,

Seems reasonable, but should it be in __vfio_pci_memory_enabled() just
to be robust?

Jason