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

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Message-ID: <20250114133553.GB5556@nvidia.com>
Date: Tue, 14 Jan 2025 09:35:53 -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, Jun 18, 2024 at 07:28:43AM +0800, Xu Yilun wrote:

> > is needed so the secure world can prepare anything it needs prior to
> > starting the VM.
> 
> OK. From Dan's patchset there are some touch point for vendor tsm
> drivers to do secure world preparation. e.g. pci_tsm_ops::probe().
> 
> Maybe we could move to Dan's thread for discussion.
> 
> https://lore.kernel.org/linux-coco/173343739517.1074769.13134786548545925484.stgit@dwillia2-xfh.jf.intel.com/

I think Dan's series is different, any uapi from that series should
not be used in the VMM case. We need proper vfio APIs for the VMM to
use. I would expect VFIO to be calling some of that infrastructure.

Really, I don't see a clear sense of how this will look yet. AMD
provided some patches along these lines, I have not seem ARM and Intel
proposals yet, not do I sense there is alignment.

> > Setting up secure vIOMMU emulation, for instance. I
> 
> I think this could be done at VM late bind time.

The vIOMMU needs to be setup before the VM boots

> > secure. This should all be pre-arranged as possible before starting
> 
> But our current implementation is not to prepare as much as possible,
> but only necessary, so most of the secure work for vPCI function is done
> at late bind time.

That's fine too, but both options need to be valid.

Jason