From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH v2] x86: avoid flush IPI when possible
Date: Wed, 17 Feb 2016 14:48:41 +0000
Message-ID: <56C48849.4000801@citrix.com>
References: <56C304A502000078000D2879@prv-mh.provo.novell.com>
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To: Jan Beulich <JBeulich@suse.com>, xen-devel <xen-devel@lists.xenproject.org>
Cc: Keir Fraser <keir@xen.org>
List-Id: xen-devel@lists.xenproject.org

On 16/02/16 10:14, Jan Beulich wrote:
> --- a/xen/arch/x86/smp.c
> +++ b/xen/arch/x86/smp.c
> @@ -205,26 +205,30 @@ static unsigned int flush_flags;
>  
>  void invalidate_interrupt(struct cpu_user_regs *regs)
>  {
> +    unsigned int flags = flush_flags;
>      ack_APIC_irq();
>      perfc_incr(ipis);
> -    if ( !__sync_local_execstate() ||
> -         (flush_flags & (FLUSH_TLB_GLOBAL | FLUSH_CACHE)) )
> -        flush_area_local(flush_va, flush_flags);
> +    if ( __sync_local_execstate() )
> +        flags &= ~FLUSH_TLB;

If a switch happened, write_ptbase() also flushed global mappings.  I
believe you can also mask out FLUSH_TLB_GLOBAL here.

Otherwise, the rest looks ok.  Reviewed-by: Andrew Cooper
<andrew.cooper3@citrix.com>