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Date: Thu, 24 Aug 2017 18:06:51 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
        xen-devel@lists.xenproject.org, Thomas Gleixner <tglx@linutronix.de>,
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        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Andrew Cooper <andrew.cooper3@citrix.com>,
        Andy Lutomirski <luto@amacapital.net>
Subject: Re: [PATCH v2] x86: enable RCU based table free
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On Thu, Aug 24, 2017 at 05:27:21PM +0200, Vitaly Kuznetsov wrote:
> Do you think adding something like
> 
> /*
>  * While x86 architecture in general requires an IPI to perform TLB
>  * shootdown, enablement code for several hypervisors overrides
>  * .flush_tlb_others hook in pv_mmu_ops and implements it by issuing
>  * a hypercall. To keep software pagetable walkers safe in this case we 
>  * switch to RCU based table free (HAVE_RCU_TABLE_FREE). See the comment
>  * below 'ifdef CONFIG_HAVE_RCU_TABLE_FREE' in include/asm-generic/tlb.h
>  * for more details.
>  */
> 
> before __tlb_remove_table would suffice? Or do you see a better place
> for such comment?

Yes, that seems fine. Thanks!