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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YgKF2NDMURGq1JD1@otcwcpicx3.sc.intel.com>
Date:   Tue, 8 Feb 2022 07:01:44 -0800
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Joerg Roedel <joro@...tes.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        iommu@...ts.linux-foundation.org, x86 <x86@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID
 allocation and free it on mm exit

On Tue, Feb 08, 2022 at 10:41:39AM +0800, Lu Baolu wrote:
> On 2/8/22 7:02 AM, Fenghua Yu wrote:
> > PASIDs are process wide. It was attempted to use refcounted PASIDs to
> > free them when the last thread drops the refcount. This turned out to
> > be complex and error prone. Given the fact that the PASID space is 20
> > bits, which allows up to 1M processes to have a PASID associated
> > concurrently, PASID resource exhaustion is not a realistic concern.
> > 
> > Therefore it was decided to simplify the approach and stick with lazy
> > on demand PASID allocation, but drop the eager free approach and make
> > a allocated PASID lifetime bound to the life time of the process.
> > 
> > Get rid of the refcounting mechanisms and replace/rename the interfaces
> > to reflect this new approach.
> > 
> > Suggested-by: Dave Hansen <dave.hansen@...ux.intel.com>
> > Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> > Reviewed-by: Tony Luck <tony.luck@...el.com>
> > ---
> > v4:
> > - Update the commit message (Thomas).
> 
> Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>

Thank you very much for your review, Baolu!

-Fenghua