linux-kernel - Re: [PATCH v7 2/8] x86/flush_tlb: try flush_tlb_single one by one in flush_tlb

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Date:	Wed, 23 May 2012 15:51:02 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Alex Shi" <alex.shi@...el.com>
Cc:	<borislav.petkov@....com>, <arnd@...db.de>,
	<a.p.zijlstra@...llo.nl>, <akinobu.mita@...il.com>,
	<eric.dumazet@...il.com>, <fweisbec@...il.com>,
	<rostedt@...dmis.org>, <hughd@...gle.com>, <jeremy@...p.org>,
	<len.brown@...el.com>, <tony.luck@...el.com>,
	<yongjie.ren@...el.com>, <kamezawa.hiroyu@...fujitsu.com>,
	<seto.hidetoshi@...fujitsu.com>, <penberg@...nel.org>,
	<yinghai@...nel.org>, <tglx@...utronix.de>,
	<akpm@...ux-foundation.org>, <ak@...ux.intel.com>, <luto@....edu>,
	<avi@...hat.com>, <dhowells@...hat.com>, <mingo@...hat.com>,
	<riel@...hat.com>, <cpw@....com>, <steiner@....com>,
	<linux-kernel@...r.kernel.org>, <viro@...iv.linux.org.uk>,
	<hpa@...or.com>
Subject: Re: [PATCH v7 2/8] x86/flush_tlb: try flush_tlb_single one by
 one in flush_tlb_range

>>> On 23.05.12 at 16:15, Alex Shi <alex.shi@...el.com> wrote:
> @@ -1269,11 +1270,11 @@ static void xen_flush_tlb_others(const struct cpumask *cpus,
>  	cpumask_and(to_cpumask(args->mask), cpus, cpu_online_mask);
>  	cpumask_clear_cpu(smp_processor_id(), to_cpumask(args->mask));
>  
> -	if (va == TLB_FLUSH_ALL) {
> +	if (start == TLB_FLUSH_ALL) {
>  		args->op.cmd = MMUEXT_TLB_FLUSH_MULTI;
>  	} else {
>  		args->op.cmd = MMUEXT_INVLPG_MULTI;
> -		args->op.arg1.linear_addr = va;
> +		args->op.arg1.linear_addr = start;
>  	}
>  
>  	MULTI_mmuext_op(mcs.mc, &args->op, 1, NULL, DOMID_SELF);

Unless there is an implicit assumption that 'start' and 'end' are on
the same page (which I doubt, as then it would be pointless to
add 'end' here), this one is definitely wrong - you'd either have
to issue multiple MMUEXT_INVLPG_MULTI-s, or you'd have to
also use MMUEXT_TLB_FLUSH_MULTI for the multi-page case.

The same would appear to apply to the UV case, albeit I don't
know enough about that code to be certain.

Jan

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