Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Message-ID: <2cd3132b-2c24-610e-1a96-591f2803404c@intel.com>
Date:   Tue, 12 Apr 2022 07:39:10 -0700
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.7.0
Content-Language: en-US
To:     Fenghua Yu <fenghua.yu@intel.com>,
        "zhangfei.gao@foxmail.com" <zhangfei.gao@foxmail.com>
Cc:     Joerg Roedel <joro@8bytes.org>,
        jean-philippe <jean-philippe@linaro.org>,
        Ravi V Shankar <ravi.v.shankar@intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Ashok Raj <ashok.raj@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        x86 <x86@kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        iommu <iommu@lists.linux-foundation.org>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Andy Lutomirski <luto@kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>
References: <20220207230254.3342514-1-fenghua.yu@intel.com>
 <20220207230254.3342514-6-fenghua.yu@intel.com> <Ygt4h0PgYzKOiB38@8bytes.org>
 <tencent_F6830A1196DB4C6A904D7C691F0D961D1108@qq.com>
 <56ed509d-a7cf-1fde-676c-a28eb204989b@intel.com>
 <tencent_9920B633D50E9B80D3A41A723BCE06972309@qq.com>
 <f439dde5-0eaa-52e4-9cf7-2ed1f62ea07f@intel.com>
 <tencent_F73C11A7DBAC6AF24D3369DF0DCA1D7E8308@qq.com>
 <a139dbad-2f42-913b-677c-ef35f1eebfed@intel.com>
 <tencent_B683AC1146DB6A6ABB4D73697C0D6A1D7608@qq.com>
 <YlWBkyGeb2ZOGLKl@fyu1.sc.intel.com>
From:   Dave Hansen <dave.hansen@intel.com>
Subject: Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID
 allocation and free it on mm exit
In-Reply-To: <YlWBkyGeb2ZOGLKl@fyu1.sc.intel.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 4/12/22 06:41, Fenghua Yu wrote:
>> master process quit, mmput ->  mm_pasid_drop->ioasid_free
>> But this ignore driver's iommu_sva_unbind_device function,
>> iommu_sva_bind_device and iommu_sva_unbind_device are not pair,  So driver
>> does not know ioasid is freed.
>>
>> Any suggestion?
> ioasid is per process or per mm. A daemon process shouldn't share the same 
> ioasid with any other process with even its parent process. Its parent gets
> an ioasid and frees it on exit. The ioasid is gone and shouldn't be used
> by its child process.
> 
> Each daemon process should call driver -> iommu_sva_bind_device -> ioasid_alloc
> to get its own ioasid/PASID. On daemon quit, the ioasid is freed.
> 
> That means nqnix needs to be changed.

Fenghua, please step back for a second and look at what you are saying.
 Your patch caused userspace to break.  Now, you're telling someone that
they need to go change that userspace to work around something that your
patch.  How, exactly, are you suggesting that nginx could change to fix
this?  What, specifically, was it doing with *fork()* that was wrong?

It sounds to me like you're saying that it's OK to break userspace.