linux-kernel - Re: [PATCH v7 9/9] x86/mmu: Allocate/free PASID

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Date:   Thu, 3 Sep 2020 22:34:53 +0000
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     Fenghua Yu <fenghua.yu@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Christoph Hellwig <hch@...radead.org>,
        Peter Zijlstra <peterz@...radead.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Jacob Jun Pan <jacob.jun.pan@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Sohil Mehta <sohil.mehta@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        x86 <x86@...nel.org>, iommu@...ts.linux-foundation.org
Subject: Re: [PATCH v7 9/9] x86/mmu: Allocate/free PASID

Hi, Thomas, Andy, et al,

On Thu, Aug 27, 2020 at 08:06:34AM -0700, Fenghua Yu wrote:
> A PASID is allocated for an "mm" the first time any thread binds
> to an SVM capable device and is freed from the "mm" when the SVM is
> unbound by the last thread. It's possible for the "mm" to have different
> PASID values in different binding/unbinding SVM cycles.
> 
> The mm's PASID (non-zero for valid PASID or 0 for invalid PASID) is
> propagated to per-thread PASID MSR for all threads within the mm through
> through IPI, context switch, or inherit to ensure a running thread has
> the right PASID MSR matching the mm's PASID.
> 
> Suggested-by: Andy Lutomirski <luto@...nel.org>
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> Reviewed-by: Tony Luck <tony.luck@...el.com>
> ---
> v7:
> - Don't fix up PASID in #GP. Instead, update the PASID MSR by IPI and
>   context switch after PASID allocation and free. Inherit PASID from
>   parent. (Andy)
> 
> Before v7:
> - Allocate a PASID for the mm and free it until mm exit.

This is a friendly reminder. Any comment on this series?

This patch (9/9) is essentially the only changed patch that implements
updating PASID MSR for a thread by IPI and context switch per Andy's
comment.

Thank you very much in advance!

-Fenghua