From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH] Changing the AMD IOMMU API path to work in an atomic context which is necessary for any custom drivers using the IOMMU API while holding a spinlock. Date: Tue, 25 Sep 2018 11:09:48 +0200 Message-ID: <20180925090948.k62lms4t5qduwnpo@8bytes.org> References: <1535120929-5693-1-git-send-email-murphyt7@tcd.ie> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1535120929-5693-1-git-send-email-murphyt7@tcd.ie> Sender: linux-kernel-owner@vger.kernel.org To: murphyt7@tcd.ie Cc: leo.duran@amd.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org List-Id: iommu@lists.linux-foundation.org On Fri, Aug 24, 2018 at 02:28:49PM +0000, murphyt7@tcd.ie wrote: > From: Tom Murphy > > --- > > This patch allows the IOMMU API path in the AMD driver to be called > from an atomic context. This is useful for anyone building a driver > which needs to call the IOMMU API while holding a spinlock. A bit more context would be helpful here. This is a pretty intrusive change since we will drain the memory allocators atomic pools now while building page-tables. This needs some more justification than just 'some drivers might need it'. Further, if we really address this problem it needs to happen through the IOMMU-API, because the functions you are patching are called from iommu_map()/iommu_unmap(), and these functions are allowed to sleep. So the required approach here would be to introduce something like iommu_map_atomic()/iommu_unmap_atomic() and implement call-backs for that in more than just one driver. Regards, Joerg