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 64CB5C433FE for ; Fri, 29 Apr 2022 22:19:15 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id E99E441D5D; Fri, 29 Apr 2022 22:19:14 +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 7LCK6p07j_VY; Fri, 29 Apr 2022 22:19:14 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp4.osuosl.org (Postfix) with ESMTPS id 8C67D41D42; Fri, 29 Apr 2022 22:19:13 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 5B9CEC0039; Fri, 29 Apr 2022 22:19:13 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id DB9FEC002D for ; Fri, 29 Apr 2022 22:19:11 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id B4B9440142 for ; Fri, 29 Apr 2022 22:19:11 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Authentication-Results: smtp2.osuosl.org (amavisd-new); dkim=pass (2048-bit key) header.d=intel.com Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 9ld87kfCbbD2 for ; Fri, 29 Apr 2022 22:19:10 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by smtp2.osuosl.org (Postfix) with ESMTPS id B2D5F4002B for ; Fri, 29 Apr 2022 22:19:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1651270750; x=1682806750; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=aAa0fJ78qBc0C3dnZn0iaoTUqMqzLiZJoB88GhSk4m8=; b=LwORgXpE62oWeA/Q/XKZAW1SFFqgBKnjt9TDRlz3gaA44yZdF3qZ+kEQ g2GVulh25ufp6jzfLyuhE1AvoU+OwteMfpoAlamOl0Hb1uL6KcLTQlytx qhBeBMYyjRtfejE3+xZnRr6+ow3mjbPPYV4TpyZ66ja5rryWRxGgzTABA 9LocB4qPy/AgKVDRx82nnTMHCmMeTQ3BedUbrNrVBzQVCS9BgP2u7T6Hp hqZog7n3wE6M5ADvNNmpJSPAnaOqwvetc8q8M3G63VQub9kNG/QueDlmy EmnIt9R8GTU/gHt+S3BptxJc8NvDddM3eyQeokbDFgUvG2KA0sG9wWMoA w==; X-IronPort-AV: E=McAfee;i="6400,9594,10332"; a="264370522" X-IronPort-AV: E=Sophos;i="5.91,186,1647327600"; d="scan'208";a="264370522" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Apr 2022 15:19:09 -0700 X-IronPort-AV: E=Sophos;i="5.91,186,1647327600"; d="scan'208";a="597551432" Received: from fyu1.sc.intel.com ([172.25.103.126]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Apr 2022 15:19:09 -0700 Date: Fri, 29 Apr 2022 15:19:39 -0700 From: Fenghua Yu To: Jean-Philippe Brucker 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: <22b659c7-e972-7a56-2bd7-8df3b4820d4e@intel.com> <8c044e49-74bb-df56-8a60-663013c0910e@intel.com> <63582490-a794-fd11-0380-44b27cc660b7@intel.com> <044595e6-e5d0-26c2-af8e-fc9d06906179@linux.intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Cc: Ravi V Shankar , Tony Luck , Ashok Raj , Peter Zijlstra , will@kernel.org, Dave Hansen , x86 , linux-kernel , Dave Hansen , iommu , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Josh Poimboeuf , zhangfei.gao@linaro.org, Thomas Gleixner , robin.murphy@arm.com 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" Hi, Jean and Baolu, On Fri, Apr 29, 2022 at 03:34:36PM +0100, Jean-Philippe Brucker wrote: > On Fri, Apr 29, 2022 at 06:51:17AM -0700, Fenghua Yu wrote: > > Hi, Baolu, > > > > On Fri, Apr 29, 2022 at 03:53:57PM +0800, Baolu Lu wrote: > > > On 2022/4/28 16:39, Jean-Philippe Brucker wrote: > > > > > The address space is what the OOM killer is after. That gets refcounted > > > > > with mmget()/mmput()/mm->mm_users. The OOM killer is satiated by the > > > > > page freeing done in __mmput()->exit_mmap(). > > > > > > > > > > Also, all the VMAs should be gone after exit_mmap(). So, even if > > > > > vma->vm_file was holding a reference to a device driver, that reference > > > > > should be gone by the time __mmdrop() is actually freeing the PASID. > > > > > > > > I agree with all that. The concern was about tearing down the PASID in the > > > > IOMMU and device from the release() MMU notifier, which would happen in > > > > exit_mmap(). But doing the teardown at or before __mmdrop() is fine. And > > > > since the IOMMU drivers need to hold mm->mm_count anyway between bind() > > > > and unbind(), I think Fenghua's fix works. > > > > > > But I didn't find mmgrab()/mmdrop() get called in both arm and intel > > > IOMMU drivers. > > > > > > $ git grep mmgrab drivers/iommu/ > > > [no output] > > > > > > Do we need to add these in a separated fix patch, or I missed anything > > > here? > > > > On both ARM and X86, sva_bind() calls mmu_notifier_register()->mmgrab() and > > sva_unbind() calls mmu_notifier_unregister()/mmu_notifier_put()->mmdrop(). > > Yes, although for Arm I realized the mmu_notifier grab wasn't sufficient > so I sent a separate fix that should go in 5.18 as well > https://lore.kernel.org/linux-iommu/20220426130444.300556-1-jean-philippe@linaro.org/ > The Arm driver still touches the arch mm context after mmu_notifier_put(). > I don't think X86 has that problem. I think so too. On X86, the mm is not used after mmu_notifier_unregister(). In case of supervisor mode SVM (i.e. svm is bound to init_mm), the code is right too because init_mm and its PASID cannot be dropped and mmu_notifier_register()/mmu_notifier_unregister() are not called. So I think no extra fix patch is needed on X86. Thanks. -Fenghua _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu