linux-kernel - Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit

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Message-ID: <YnDeoGjv/dZnu+YQ@myrica>
Date:   Tue, 3 May 2022 08:49:52 +0100
From:   Jean-Philippe Brucker <jean-philippe@...aro.org>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Peter Zijlstra <peterz@...radead.org>, robin.murphy@....com,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        x86 <x86@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        iommu <iommu@...ts.linux-foundation.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>, zhangfei.gao@...aro.org,
        Thomas Gleixner <tglx@...utronix.de>, will@...nel.org
Subject: Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID
 allocation and free it on mm exit

On Sat, Apr 30, 2022 at 03:33:17PM +0800, Baolu Lu wrote:
> Jean, another quick question about the iommu_sva_bind_device()
> 
> /**
>  * iommu_sva_bind_device() - Bind a process address space to a device
>  * @dev: the device
>  * @mm: the mm to bind, caller must hold a reference to it
>  * @drvdata: opaque data pointer to pass to bind callback
> 
> This interface requires the caller to take a reference to mm. Which
> reference should it take, mm->mm_count or mm->mm_users? It's better to
> make it explicit in this comment.

Agreed, it's mm_users as required by mmu_notifier_register()

Thanks,
Jean