From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jerome Glisse Subject: Re: [PATCH] iommu/amd: Fix amd_iommu_detect() (does not fix any issues). Date: Tue, 27 Oct 2015 09:53:30 +0900 Message-ID: <20151027005329.GB3569@gmail.com> References: <1441059183-9023-1-git-send-email-j.glisse@gmail.com> <20151026160717.GF5618@l.oracle.com> <20151027004747.GA3569@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: <20151027004747.GA3569-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Konrad Rzeszutek Wilk Cc: =?iso-8859-1?B?Suly9G1l?= Glisse , Joerg Roedel , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org List-Id: iommu@lists.linux-foundation.org On Tue, Oct 27, 2015 at 09:47:48AM +0900, Jerome Glisse wrote: > On Mon, Oct 26, 2015 at 12:07:17PM -0400, Konrad Rzeszutek Wilk wrote: > > On Mon, Aug 31, 2015 at 06:13:03PM -0400, j.glisse-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org wrote: > > > From: J=E9r=F4me Glisse > > > = > > > Fix amd_iommu_detect() to return positive value on success, like > > > intended, and not zero. This will not change anything in the end > > > as AMD IOMMU disable swiotlb and properly associate itself with > > = > > Not sure how it disables SWIOTLB? The AMD Vi does not seem to > > change 'swiotlb'. While 'gart_iommu_init' does. Did you mean > > the AMD GART code? > = > So this is convoluted and painfull, each i look back at that it takes > me time to figure out of thing happen. Basicly amd_iommu_init_dma_ops() > will replace dma_ops to no_mmu unless passthrough, and when the AMD > iommu associate itself with each device it will set the archdata.dma_ops > again this unbind the default of swiotlb that is initialize before > hw IOMMU. > = > > = > > > devices even if detect() doesn't return a positive value. > > = > > Returning positive will mean that the pci_iommu_alloc will stop > > processing _all_ other IOMMUs. > > > > While returning 0 will let it detect the other IOMMUs. > = > No see the IOMMU_FINISH_IF_DETECTED flags in pci_iommu_alloc(). > Which is not set for AMD hence my patch should not change anything > it (AFAICT and from testing but i do not have all AMD hw the ever > existed). > = > So i am just making the detect function do what the API doc says it > should do. See line 72 to 80 of : arch/x86/include/asm/iommu_table.h > = > > = > > Granted on an AMD machine there can be two 'IOMMU's - the GART > > and the AMD Vi. The detection is always to call gart_iommu_hole_init > > first, then amd_iommu_detect. > > = > > I presume if there was one more type on AMD we would run into trouble. > = > No because of IOMMU_FINISH_IF_DETECTED flag. > = > Hope this clarify thing this spagethi mix :) Ok my bad amd actualy is using IOMMU_INIT_FINISH() so it finish before trying other. Which make sense for AMD as AMD driver will call the gart init gart_iommu_init() if it fails to initialize. If we ever end up with a platform with multiple IOMMU beside AMD then we need to switch to the IOMMU_INIT() instead of the finish one. Cheers, J=E9r=F4me