linux-kernel - Re: [PATCH 1/2] mm: Add kernel MMU notifier to manage IOTLB/DEVTLB

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Date:   Thu, 14 Dec 2017 14:43:27 +0800
From:   "Huang\, Ying" <ying.huang@...el.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Lu Baolu <baolu.lu@...ux.intel.com>, Bob Liu <liubo95@...wei.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        "Joerg Roedel" <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Rik van Riel <riel@...hat.com>,
        Michal Hocko <mhocko@...e.com>,
        Dave Jiang <dave.jiang@...el.com>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <iommu@...ts.linux-foundation.org>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Matthew Wilcox <willy@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Kees Cook <keescook@...omium.org>,
        "xieyisheng \(A\)" <xieyisheng1@...wei.com>
Subject: Re: [PATCH 1/2] mm: Add kernel MMU notifier to manage IOTLB/DEVTLB

Hi, Dave,

Dave Hansen <dave.hansen@...el.com> writes:

> On 12/13/2017 07:38 PM, Lu Baolu wrote:
>> 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.
>
> What's the plan to deal with all of the ways other than vmalloc() that
> the kernel changes the page tables?

The kernel MMU notifier is called in flush_tlb_kernel_range().  So IOMMU
will be notified for TLB flushing caused by all ways that the kernel
changes the page tables including vmalloc, kmap, etc.

Best Regards,
Huang, Ying