Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:18 as permitted sender) client-ip=2620:137:e000::1:18;
MIME-Version: 1.0
References: <165201148069.536527.1960632033331546251.tglx@xen13> <CAHk-=wjMmSZzMJ3Xnskdg4+GGz=5p5p+GSYyFBTh0f-DgvdBWg@mail.gmail.com>
In-Reply-To: <CAHk-=wjMmSZzMJ3Xnskdg4+GGz=5p5p+GSYyFBTh0f-DgvdBWg@mail.gmail.com>
From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sun, 8 May 2022 11:09:48 -0700
Message-ID: <CAHk-=whj6m0B9ys4XyE4AAPPoXE7XpBtxL7mD3Rk6EYX1=Ugng@mail.gmail.com>
Subject: Re: [GIT pull] core/urgent for v5.18-rc6
To:     Thomas Gleixner <tglx@linutronix.de>,
        Zhangfei Gao <zhangfei.gao@foxmail.com>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        Jacob Pan <jacob.jun.pan@linux.intel.com>,
        Dave Hansen <dave.hansen@intel.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "the arch/x86 maintainers" <x86@kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Sun, May 8, 2022 at 11:00 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> I suspect it's related to mmu_notifiers or something, but I really
> would have liked a more exact "this is where things go wrong".

Looks like it is

 ->(*sva_bind)()
    -> intel_svm_bind_mm()
      -> mmu_notifier_register(&svm->notifier, mm)

and yes, the mmu notifiers annoyingly end up doing an mmgrab, because
they actually don't want to affect the state of mm teardown, they just
want to be notified about it.

Annoying, but it seems to explain the issue if I followed this right.

Unlike the commit message.

                Linus