linux-kernel - Re: [RFC PATCH v2 55/58] drivers/iommu: Add deferred map

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250103154757.GG26854@ziepe.ca>
Date: Fri, 3 Jan 2025 11:47:57 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Mostafa Saleh <smostafa@...gle.com>
Cc: Robin Murphy <robin.murphy@....com>, iommu@...ts.linux.dev,
	kvmarm@...ts.linux.dev, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, catalin.marinas@....com,
	will@...nel.org, maz@...nel.org, oliver.upton@...ux.dev,
	joey.gouly@....com, suzuki.poulose@....com, yuzenghui@...wei.com,
	robdclark@...il.com, joro@...tes.org, jean-philippe@...aro.org,
	nicolinc@...dia.com, vdonnefort@...gle.com, qperret@...gle.com,
	tabba@...gle.com, danielmentz@...gle.com, tzukui@...gle.com
Subject: Re: [RFC PATCH v2 55/58] drivers/iommu: Add deferred map_sg
 operations

On Fri, Jan 03, 2025 at 03:35:20PM +0000, Mostafa Saleh wrote:

> An alternative approach as Robin suggested, is to treat all iommu_map as sg map,
> and when the driver gets the iotlb_sync_map() call it can just issue the hypercall,
> however this call only provides the IOVA range, which requires extra work or locking
> as mentioned in the thread, and as Robin mentioned s390 doing something similar,
> I was highlighting that in their driver, this call only notifies the hypervisor
> about an IOVA and not an actual pv map as pKVM, so it much simpler in their case.

Oh, that is much clearer, maybe incorporate some of that into the
commit message.

We are going in a general direction of trying to make the fast dma
mapping path not require sg, so adding sg specific optimizations to
the low level driver is not good.

Batching the hypercalls in the gather and then flushing to execute the
batch seems more reasonable.

You could probably work on advancing this infrastructure separately
via virtio-iommu..

Jason