From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [PATCH 5/5] iommu: Allow default domain type to be set on the kernel command line Date: Thu, 26 Jan 2017 17:26:32 +0000 Message-ID: <5717f26c-44ee-2057-e7dc-8dca42e3cd88@arm.com> References: <1484849955-1871-1-git-send-email-will.deacon@arm.com> <1484849955-1871-6-git-send-email-will.deacon@arm.com> <20170126171555.GD27598@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20170126171555.GD27598-zLv9SwRftAIdnm+yROfE0A@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: Joerg Roedel , Will Deacon Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: iommu@lists.linux-foundation.org On 26/01/17 17:15, Joerg Roedel wrote: > On Thu, Jan 19, 2017 at 06:19:15PM +0000, Will Deacon wrote: >> Rather than modify each IOMMU driver to provide different semantics for >> DMA domains, instead we introduce a command line parameter that can be >> used to change the type of the default domain. Passthrough can then be >> specified using "iommu.default_domain=identity" on the kernel command >> line. > > I like the general idea of this, but the above is a terrible name for a > kernel commandline-parameter. The x86 iommus support iommu=pt which is > pretty much the same as this patch does. Indeed, I was keen on making "iommu=pt" also do this default domain switch itself so we wouldn't need a new option - it didn't *appear* that that would break the AMD driver (as the only other default domain user supporting identity domains) but I may have overlooked something. Robin. > How about something like "iommu.passthrough=0/1"? And please add the > parameter to the kernel documentation too. > > > Joerg > From mboxrd@z Thu Jan 1 00:00:00 1970 From: robin.murphy@arm.com (Robin Murphy) Date: Thu, 26 Jan 2017 17:26:32 +0000 Subject: [PATCH 5/5] iommu: Allow default domain type to be set on the kernel command line In-Reply-To: <20170126171555.GD27598@8bytes.org> References: <1484849955-1871-1-git-send-email-will.deacon@arm.com> <1484849955-1871-6-git-send-email-will.deacon@arm.com> <20170126171555.GD27598@8bytes.org> Message-ID: <5717f26c-44ee-2057-e7dc-8dca42e3cd88@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 26/01/17 17:15, Joerg Roedel wrote: > On Thu, Jan 19, 2017 at 06:19:15PM +0000, Will Deacon wrote: >> Rather than modify each IOMMU driver to provide different semantics for >> DMA domains, instead we introduce a command line parameter that can be >> used to change the type of the default domain. Passthrough can then be >> specified using "iommu.default_domain=identity" on the kernel command >> line. > > I like the general idea of this, but the above is a terrible name for a > kernel commandline-parameter. The x86 iommus support iommu=pt which is > pretty much the same as this patch does. Indeed, I was keen on making "iommu=pt" also do this default domain switch itself so we wouldn't need a new option - it didn't *appear* that that would break the AMD driver (as the only other default domain user supporting identity domains) but I may have overlooked something. Robin. > How about something like "iommu.passthrough=0/1"? And please add the > parameter to the kernel documentation too. > > > Joerg >