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[209.6.200.48]) by smtp.gmail.com with ESMTPSA id c188sm4304725qkg.92.2018.01.26.20.24.15 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 26 Jan 2018 20:24:16 -0800 (PST) Date: Fri, 26 Jan 2018 23:24:13 -0500 From: Konrad Rzeszutek Wilk To: Josh Poimboeuf Cc: David Woodhouse , Peter Zijlstra , Andi Kleen , Paul Turner , LKML , Linus Torvalds , Greg Kroah-Hartman , Tim Chen , Dave Hansen , tglx@linutronix.de, Kees Cook , Rik van Riel , Andy Lutomirski , Jiri Kosina , 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) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: 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?