linux-kernel - Re: [RFC PATCH 08/12] vfio/pci: Create host unaccessible dma-buf for private device

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Message-ID: <20250108133026.GQ5556@nvidia.com>
Date: Wed, 8 Jan 2025 09:30:26 -0400
From: Jason Gunthorpe <jgg@...dia.com>
To: Xu Yilun <yilun.xu@...ux.intel.com>
Cc: kvm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org,
	sumit.semwal@...aro.org, christian.koenig@....com,
	pbonzini@...hat.com, seanjc@...gle.com, alex.williamson@...hat.com,
	vivek.kasireddy@...el.com, dan.j.williams@...el.com, aik@....com,
	yilun.xu@...el.com, linux-coco@...ts.linux.dev,
	linux-kernel@...r.kernel.org, lukas@...ner.de, yan.y.zhao@...el.com,
	daniel.vetter@...ll.ch, leon@...nel.org, baolu.lu@...ux.intel.com,
	zhenzhong.duan@...el.com, tao1.su@...el.com
Subject: Re: [RFC PATCH 08/12] vfio/pci: Create host unaccessible dma-buf for
 private device

On Tue, Jan 07, 2025 at 10:27:15PM +0800, Xu Yilun wrote:
> Add a flag for ioctl(VFIO_DEVICE_BIND_IOMMUFD) to mark a device as
> for private assignment. For these private assigned devices, disallow
> host accessing their MMIO resources.

Why? Shouldn't the VMM simply not call mmap? Why does the kernel have
to enforce this?

Jason