linux-kernel - Re: [REF PATCH] x86/tlb: just do tlb flush on one of siblings of SMT

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Date:	Tue, 5 Apr 2016 21:47:23 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Alex Shi <alex.shi@...aro.org>
Cc:	X86 ML <x86@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
	<linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>, Rik van Riel <riel@...hat.com>
Subject: Re: [REF PATCH] x86/tlb: just do tlb flush on one of siblings of SMT

On Apr 5, 2016 8:17 PM, "Alex Shi" <alex.shi@...aro.org> wrote:
>
> It seems Intel core still share the TLB pool, flush both of threads' TLB
> just cause a extra useless IPI and a extra flush. The extra flush will
> flush out TLB again which another thread just introduced.
> That's double waste.

Do you have a reference in both the SDM and the APM for this?

Do we have a guarantee that this serialized the front end such that
the non-targetted sibling won't execute an instruction that it decoded
from a stale translation?

This will conflict rather deeply with my PCID series, too.

--Andy