From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <konrad.r.wilk@gmail.com>
ARC-Seal: i=1; a=rsa-sha256; t=1517027057; cv=none;
        d=google.com; s=arc-20160816;
        b=yLXmoNi/qtPll9ECHBkUvJRv4xNIldyPmbclFsiGQyxqTi6/Lm1uMhrnOYIeeLIFN3
         VE3qw85xMRbsBhx9UU8BVLyDtY/uZc4nwYX8cMjcGEobDSOSSAC+oOI64g8eHFhPeMAP
         w/zd0MRvCTyg6zK1FYXwQOw88HPD07POacjM9EMRDa0JQjwPa0yjhNJCi5HoUlh43UC4
         7B+QL4CJihom2qS3Z2cyQ0KQrV1hKLboufFJnWuy4qaYcPU77crYx6zzUYE30YUGM53a
         L3OSRWKCpZG07+vcTswiWix/8ewWfdBkGR2v//BDXKK0U03LyVj3htrm+C6BmSVzRgLn
         VmPQ==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816;
        h=user-agent:in-reply-to:content-disposition:mime-version:references
         :message-id:subject:cc:to:from:date:sender:dkim-signature
         :arc-authentication-results;
        bh=5EeEnlClxin5lJtgLSZCVTY3UN54ETBhHGAjeRuMzzc=;
        b=QsS4HtVVFAzZkgJsBzlLOAVh9fV3RInvnkVFuQFiWujYtBZ2iNbt81fYVeiU+WmGK7
         i8iL9Ihayx1/g0zGtKMOhdXasQCMqS0sGK6QduMZLXss/Pd2pzzS7lL6EbFYdXIuuQ29
         3mmSOizTc7srqDpawGIiCjqMwnIgayDzvuP2W6vnxnMfuJB285kVeY9ToY7wTNnAQmlG
         eUPcxF0Z0UpbkvtmWN3edyLKKkRIDNeuxZ88wZDFKhj0PgiS+AD0kxHvj5EAF1PHiD0r
         Xja5/YIgEqcpj6am5qtJYWpNOlPDP/hFRSsSKk6+aI7aG70MTVrgJ29amdFam2vcnD2l
         pQig==
ARC-Authentication-Results: i=1; mx.google.com;
       dkim=pass header.i=@gmail.com header.s=20161025 header.b=hbtpzTGx;
       spf=pass (google.com: domain of konrad.r.wilk@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=konrad.r.wilk@gmail.com
Authentication-Results: mx.google.com;
       dkim=pass header.i=@gmail.com header.s=20161025 header.b=hbtpzTGx;
       spf=pass (google.com: domain of konrad.r.wilk@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=konrad.r.wilk@gmail.com
X-Google-Smtp-Source: AH8x226zCHoJPFz/bCfV82FioovutIrRb+c5ulewJqEI4amjgRxRxYl27FGDVpdv50R4z/QktzMu0g==
Sender: Konrad Rzeszutek Wilk <konrad.r.wilk@gmail.com>
Date: Fri, 26 Jan 2018 23:24:13 -0500
From: Konrad Rzeszutek Wilk <konrad@darnok.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Andi Kleen <ak@linux.intel.com>, Paul Turner <pjt@google.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linux-foundation.org>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Dave Hansen <dave.hansen@intel.com>, tglx@linutronix.de,
	Kees Cook <keescook@google.com>, Rik van Riel <riel@redhat.com>,
	Andy Lutomirski <luto@amacapital.net>,
	Jiri Kosina <jikos@kernel.org>, gnomes@lxorguk.ukuu.org.uk,
	x86@kernel.org, bp@alien8.de, rga@amazon.de,
	thomas.lendacky@amd.com
Subject: Re: [PATCH v2.1] x86/retpoline: Fill return stack buffer on vmexit
Message-ID: <20180127042411.GB21508@localhost.localdomain>
References: <1515670638-8552-1-git-send-email-dwmw@amazon.co.uk>
 <20180111142038.sqhflhikcailqnwi@treble>
 <1515680912.22302.351.camel@infradead.org>
 <20180111143206.GA6176@hirez.programming.kicks-ass.net>
 <1515682437.22302.355.camel@infradead.org>
 <20180111150419.2nsqst6qpifeq7k5@treble>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20180111150419.2nsqst6qpifeq7k5@treble>
User-Agent: Mutt/1.9.1 (2017-09-22)
X-getmail-retrieved-from-mailbox: INBOX
X-GMAIL-THRID: =?utf-8?q?1589247701167723388?=
X-GMAIL-MSGID: =?utf-8?q?1590718164268804075?=
X-Mailing-List: linux-kernel@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>

> Looks good to me.
> 
> Another IRC discussion was that Boris may eventually add a feature to
> the alternatives code to automatically insert such a jump if there are a
> lot of nops.

I vaguely recall that NOPs are skipped by the CPU so that it shouldn't
matter as compared to say jumping over them. But is that no the case
anymore? Or is it that we have so many NOPs that the prefetcher runs
out of space and stalls?