From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B9082C433EF for ; Tue, 15 Feb 2022 09:55:26 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 5972D4032C; Tue, 15 Feb 2022 09:55:26 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 9__h663J741g; Tue, 15 Feb 2022 09:55:25 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp4.osuosl.org (Postfix) with ESMTPS id 37A714094C; Tue, 15 Feb 2022 09:55:25 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 0D325C0011; Tue, 15 Feb 2022 09:55:25 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [IPv6:2605:bc80:3010::137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 13352C000B for ; Tue, 15 Feb 2022 09:55:24 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id E84314094C for ; Tue, 15 Feb 2022 09:55:23 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id BqJR6Hef_BRR for ; Tue, 15 Feb 2022 09:55:23 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.8.0 Received: from theia.8bytes.org (8bytes.org [IPv6:2a01:238:4383:600:38bc:a715:4b6d:a889]) by smtp4.osuosl.org (Postfix) with ESMTPS id 5C42C4032C for ; Tue, 15 Feb 2022 09:55:23 +0000 (UTC) Received: by theia.8bytes.org (Postfix, from userid 1000) id F22B836D; Tue, 15 Feb 2022 10:55:20 +0100 (CET) Date: Tue, 15 Feb 2022 10:55:19 +0100 From: Joerg Roedel To: Fenghua Yu Subject: Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit Message-ID: References: <20220207230254.3342514-1-fenghua.yu@intel.com> <20220207230254.3342514-6-fenghua.yu@intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220207230254.3342514-6-fenghua.yu@intel.com> Cc: Ravi V Shankar , Tony Luck , Ashok Raj , Peter Zijlstra , Dave Hansen , x86 , linux-kernel , iommu@lists.linux-foundation.org, Ingo Molnar , Borislav Petkov , Andy Lutomirski , Josh Poimboeuf , Thomas Gleixner X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Mon, Feb 07, 2022 at 03:02:48PM -0800, Fenghua Yu wrote: > PASIDs are process wide. It was attempted to use refcounted PASIDs to > free them when the last thread drops the refcount. This turned out to > be complex and error prone. Given the fact that the PASID space is 20 > bits, which allows up to 1M processes to have a PASID associated > concurrently, PASID resource exhaustion is not a realistic concern. > > Therefore it was decided to simplify the approach and stick with lazy > on demand PASID allocation, but drop the eager free approach and make > a allocated PASID lifetime bound to the life time of the process. > > Get rid of the refcounting mechanisms and replace/rename the interfaces > to reflect this new approach. > > Suggested-by: Dave Hansen > Signed-off-by: Fenghua Yu > Reviewed-by: Tony Luck Acked-by: Joerg Roedel _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu