Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 4 Oct 2001 06:11:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 4 Oct 2001 06:10:51 -0400 Received: from wiprom2mx1.wipro.com ([203.197.164.41]:51680 "EHLO wiprom2mx1.wipro.com") by vger.kernel.org with ESMTP id ; Thu, 4 Oct 2001 06:10:37 -0400 Message-ID: <3BBC35BC.5020706@wipro.com> Date: Thu, 04 Oct 2001 15:41:08 +0530 From: "BALBIR SINGH" User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:0.9.4) Gecko/20010913 X-Accept-Language: en-us MIME-Version: 1.0 To: "David S. Miller" CC: James.Bottomley@HansenPartnership.com, jes@sunsite.dk, linuxopinion@yahoo.com, linux-kernel@vger.kernel.org Subject: Re: how to get virtual address from dma address In-Reply-To: <200110032244.f93MiI103485@localhost.localdomain> <20011003.172439.66056954.davem@redhat.com> Content-Type: multipart/mixed; boundary="------------InterScan_NT_MIME_Boundary" Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------InterScan_NT_MIME_Boundary Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit With Rik's reverse mapping patch, wouldn't we have the virtual address for the given physical address ? I have no clue about how the patch works, somebody willing to explain it? Balbir David S. Miller wrote: > From: James Bottomley > Date: Wed, 03 Oct 2001 17:44:18 -0500 > > (although I can see it may be expensive to walk iommu page tables) > >I know of hardware where doing the reverse mapping would not even be >possible, the page tables are in hardware registers and are "write >only". This means you can't even read the PTEs back, you'd have to >keep track of them in software and that is totally unacceptable >overhead when it won't even be used %99 of the time. > >The DMA API allows us to support such hardware cleanly and >efficiently, but once we add this feature which "everyone absolutely >needs" we have a problem with the above mentioned piece of hardware. > >Franks a lot, >David S. Miller >davem@redhat.com > >- >To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >the body of a message to majordomo@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html >Please read the FAQ at http://www.tux.org/lkml/ > --------------InterScan_NT_MIME_Boundary Content-Type: text/plain; name="Wipro_Disclaimer.txt" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="Wipro_Disclaimer.txt" ---------------------------------------------------------------------------------------------------------------------- Information transmitted by this E-MAIL is proprietary to Wipro and/or its Customers and is intended for use only by the individual or entity to which it is addressed, and may contain information that is privileged, confidential or exempt from disclosure under applicable law. If you are not the intended recipient or it appears that this mail has been forwarded to you without proper authority, you are notified that any use or dissemination of this information in any manner is strictly prohibited. In such cases, please notify us immediately at mailto:mailadmin@wipro.com and delete this mail from your records. ---------------------------------------------------------------------------------------------------------------------- --------------InterScan_NT_MIME_Boundary-- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/