linux-kernel - Re: [PATCH v6 10/11] vfio/pci: Add dma-buf export support for MMIO regions

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Message-Id: <d757cbcb-866a-4af4-b4fd-0ba27f706e74@app.fastmail.com>
Date: Sun, 02 Nov 2025 19:16:34 +0200
From: "Leon Romanovsky" <leon@...nel.org>
To: "Alex Williamson" <alex@...zbot.org>
Cc: "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>,
 "Jason Gunthorpe" <jgg@...pe.ca>,
 "Andrew Morton" <akpm@...ux-foundation.org>,
 "Jonathan Corbet" <corbet@....net>,
 "Sumit Semwal" <sumit.semwal@...aro.org>,
 Christian König <christian.koenig@....com>,
 "Alex Williamson" <alex.williamson@...hat.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 v6 10/11] vfio/pci: Add dma-buf export support for MMIO regions

On Sun, Nov 2, 2025, at 19:11, Alex Williamson wrote:
> On Sun, 2 Nov 2025 17:12:53 +0200
> Leon Romanovsky <leon@...nel.org> wrote:
>> On Sun, Nov 02, 2025 at 08:01:37AM -0700, Alex Williamson wrote: 
>> > We don't need the separate loop or flag, and adding it breaks the
>> > existing reverse list walk.  Thanks,  
>> 
>> Do you want me to send v7? I have a feeling that v6 is good to be merged.
>
> Let's hold off, if this ends up being the only fixup I can roll it in.
> Thanks,

Thanks 

>
> Alex
> 
>> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
>> index 24204893e221..51a3bcc26f8b 100644
>> --- a/drivers/vfio/pci/vfio_pci_core.c
>> +++ b/drivers/vfio/pci/vfio_pci_core.c
>> @@ -2403,7 +2403,6 @@ static int vfio_pci_dev_set_hot_reset(struct vfio_device_set *dev_set,
>>                                       struct iommufd_ctx *iommufd_ctx)
>>  {
>>         struct vfio_pci_core_device *vdev;
>> -       bool restore_revoke = false;
>>         struct pci_dev *pdev;
>>         int ret;
>>  
>> @@ -2473,7 +2472,6 @@ static int vfio_pci_dev_set_hot_reset(struct vfio_device_set *dev_set,
>>                 }
>>  
>>                 vfio_pci_dma_buf_move(vdev, true);
>> -               restore_revoke = true;
>>                 vfio_pci_zap_bars(vdev);
>>         }
>>  
>> @@ -2501,15 +2499,12 @@ static int vfio_pci_dev_set_hot_reset(struct vfio_device_set *dev_set,
>>                                struct vfio_pci_core_device, vdev.dev_set_list);
>>  
>>  err_undo:
>> -       if (restore_revoke) {
>> -               list_for_each_entry(vdev, &dev_set->device_list, vdev.dev_set_list)
>> -                       if (__vfio_pci_memory_enabled(vdev))
>> -                               vfio_pci_dma_buf_move(vdev, false);
>> -       }
>> -
>>         list_for_each_entry_from_reverse(vdev, &dev_set->device_list,
>> -                                        vdev.dev_set_list)
>> +                                        vdev.dev_set_list) {
>> +               if (__vfio_pci_memory_enabled(vdev))
>> +                       vfio_pci_dma_buf_move(vdev, false);
>>                 up_write(&vdev->memory_lock);
>> +       }
>>  
>>         list_for_each_entry(vdev, &dev_set->device_list, vdev.dev_set_list)
>>                 pm_runtime_put(&vdev->pdev->dev);
>> 
>> 
>> > 
>> > Alex
>> >   
>>