linux-kernel - Re: [PATCH v3 06/11] x86/mm: Rework lazy TLB mode and TLB freshness tracking

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Message-ID: <cb8aad11-6e02-bc8e-8613-63f63a22bc77@oracle.com>
Date:   Fri, 23 Jun 2017 09:34:42 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Andy Lutomirski <luto@...nel.org>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Nadav Amit <nadav.amit@...il.com>,
        Rik van Riel <riel@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Banman <abanman@....com>, Mike Travis <travis@....com>,
        Dimitri Sivanich <sivanich@....com>,
        Juergen Gross <jgross@...e.com>
Subject: Re: [PATCH v3 06/11] x86/mm: Rework lazy TLB mode and TLB freshness
 tracking


> diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
> index 1d7a7213a310..f5df56fb8b5c 100644
> --- a/arch/x86/xen/mmu_pv.c
> +++ b/arch/x86/xen/mmu_pv.c
> @@ -1005,8 +1005,7 @@ static void xen_drop_mm_ref(struct mm_struct *mm)
>   	/* Get the "official" set of cpus referring to our pagetable. */
>   	if (!alloc_cpumask_var(&mask, GFP_ATOMIC)) {
>   		for_each_online_cpu(cpu) {
> -			if (!cpumask_test_cpu(cpu, mm_cpumask(mm))
> -			    && per_cpu(xen_current_cr3, cpu) != __pa(mm->pgd))
> +			if (per_cpu(xen_current_cr3, cpu) != __pa(mm->pgd))
>   				continue;
>   			smp_call_function_single(cpu, drop_mm_ref_this_cpu, mm, 1);
>   		}
> 


I wonder then whether
	cpumask_copy(mask, mm_cpumask(mm));
immediately below is needed.

-boris