linux-kernel - Re: [PATCH v2] Linux VM workaround for Knights Landing A/D leak

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Message-ID: <20160614204736.GL30015@pd.tnic>
Date:	Tue, 14 Jun 2016 22:47:36 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Dave Hansen <dave.hansen@...ux.intel.com>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Lukasz Anaczkowski <lukasz.anaczkowski@...el.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	tglx@...utronix.de, mingo@...hat.com, ak@...ux.intel.com,
	kirill.shutemov@...ux.intel.com, mhocko@...e.com,
	akpm@...ux-foundation.org, harish.srinivasappa@...el.com,
	lukasz.odzioba@...el.com, grzegorz.andrejczuk@...el.com,
	lukasz.daniluk@...el.com
Subject: Re: [PATCH v2] Linux VM workaround for Knights Landing A/D leak

On Tue, Jun 14, 2016 at 01:20:06PM -0700, H. Peter Anvin wrote:
> static_cpu_has_bug() should turn into 5-byte NOP in the common (bugless)
> case.

Yeah, it does. I looked at the asm.

I wasn't 100% sure because I vaguely remember gcc reordering things in
some pathological case but I'm most likely remembering wrong because if
it were doing that, then the whole nopping out won't work. F'get about
it. :)

-- 
Regards/Gruss,
    Boris.

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