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

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Message-ID: <BN9PR11MB527687E27FC35CD842E4EA7B8CD99@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Thu, 9 Feb 2023 04:10:04 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Nicolin Chen <nicolinc@...dia.com>,
        "jgg@...dia.com" <jgg@...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>
CC:     "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()

> 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.