Re: Question about reserved_regions w/ Intel IOMMU

From: Alexander Duyck <alexander.duyck@gmail.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Robin Murphy <robin.murphy@arm.com>,
	"Tian, Kevin" <kevin.tian@intel.com>,
	 Alex Williamson <alex.williamson@redhat.com>,
	Baolu Lu <baolu.lu@linux.intel.com>,
	 LKML <linux-kernel@vger.kernel.org>,
	linux-pci <linux-pci@vger.kernel.org>,
	 "iommu@lists.linux.dev" <iommu@lists.linux.dev>
Subject: Re: Question about reserved_regions w/ Intel IOMMU
Date: Tue, 20 Jun 2023 10:47:09 -0700	[thread overview]
Message-ID: <CAKgT0UdbjDDkwV_uUGCTONGj2Xw_+Tb6J5enAX_+Wq0eKt=nGA@mail.gmail.com> (raw)
In-Reply-To: <ZJHaE2+XOgQj1q2k@nvidia.com>

On Tue, Jun 20, 2023 at 9:55 AM Jason Gunthorpe <jgg@nvidia.com> wrote:
>
> On Tue, Jun 20, 2023 at 07:57:57AM -0700, Alexander Duyck wrote:
>
> > I think this may have gone off down a rathole as my original question
> > wasn't anything about adding extra reserved regions. It was about
> > exposing what the IOVA is already reserving so it could be user
> > visible.
>
> Your question points out that dma-iommu.c uses a different set of
> reserved regions than everything else, and its set is closer to
> functionally correct.
>
> IMHO the resolution to what you are talking about is not to add more
> debugging to dma-iommu but to make the set of reserved regions
> consistently correct for everyone, which will make them viewable in
> sysfs.

Okay, that makes sense to me, and I agree. If we had a consistent set
of reserved regions then it would make it easier to understand. If
nothing else my request would be to expose the iova reserved regions
and then most likely the other ones could be deprecated since they
seem to all be consolidated in the IOVA anyway.

Thanks,

- Alex