From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f198.google.com (mail-wr0-f198.google.com [209.85.128.198]) by kanga.kvack.org (Postfix) with ESMTP id CAD346B0033 for ; Thu, 14 Dec 2017 01:10:41 -0500 (EST) Received: by mail-wr0-f198.google.com with SMTP id v69so2616914wrb.3 for ; Wed, 13 Dec 2017 22:10:41 -0800 (PST) Received: from szxga05-in.huawei.com (szxga05-in.huawei.com. [45.249.212.191]) by mx.google.com with ESMTPS id j15si2838552wra.472.2017.12.13.22.10.38 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 13 Dec 2017 22:10:40 -0800 (PST) Subject: Re: [PATCH 1/2] mm: Add kernel MMU notifier to manage IOTLB/DEVTLB References: <1513213366-22594-1-git-send-email-baolu.lu@linux.intel.com> <1513213366-22594-2-git-send-email-baolu.lu@linux.intel.com> <5A31F232.90901@linux.intel.com> From: Bob Liu Message-ID: Date: Thu, 14 Dec 2017 14:07:38 +0800 MIME-Version: 1.0 In-Reply-To: <5A31F232.90901@linux.intel.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Lu Baolu , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Alex Williamson , Joerg Roedel , David Woodhouse Cc: Rik van Riel , Michal Hocko , Dave Jiang , Dave Hansen , x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Vegard Nossum , Andy Lutomirski , Huang Ying , Matthew Wilcox , Andrew Morton , "Paul E . McKenney" , "Kirill A . Shutemov" , Kees Cook , "xieyisheng (A)" On 2017/12/14 11:38, Lu Baolu wrote: > Hi, > > On 12/14/2017 11:10 AM, Bob Liu wrote: >> On 2017/12/14 9:02, Lu Baolu wrote: >>>> From: Huang Ying >>>> >>>> Shared Virtual Memory (SVM) allows a kernel memory mapping to be >>>> shared between CPU and and a device which requested a supervisor >>>> PASID. Both devices and IOMMU units have TLBs that cache entries >>>> from CPU's page tables. We need to get a chance to flush them at >>>> the same time when we flush the CPU TLBs. >>>> >>>> We already have an existing MMU notifiers for userspace updates, >>>> however we lack the same thing for kernel page table updates. To >> Sorry, I didn't get which situation need this notification. >> Could you please describe the full scenario? > > Okay. > > 1. When an SVM capable driver calls intel_svm_bind_mm() with > SVM_FLAG_SUPERVISOR_MODE set in the @flags, the kernel > memory page mappings will be shared between CPUs and > the DMA remapping agent (a.k.a. IOMMU). The page table > entries will also be cached in both IOTLB (located in IOMMU) > and the DEVTLB (located in device). > But who/what kind of real device has the requirement to access a kernel VA? Looks like SVM_FLAG_SUPERVISOR_MODE is used by nobody? Cheers, Liubo > 2. When vmalloc/vfree interfaces are called, the page mappings > for kernel memory might get changed. And current code calls > flush_tlb_kernel_range() to flush CPU TLBs only. The IOTLB or > DevTLB will be stale compared to that on the cpu for kernel > mappings. > > We need a kernel mmu notification to flush TLBs in IOMMU and > devices as well. > > Best regards, > Lu Baolu > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org