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Peter Anvin" To: Thorsten Glaser , Steven Rostedt CC: Peter Zijlstra , x86@kernel.org, torvalds@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-toolchains@vger.kernel.org, jpoimboe@redhat.com, alexei.starovoitov@gmail.com, mhiramat@kernel.org Subject: Re: [PATCH 1/2] x86: Remove dynamic NOP selection User-Agent: K-9 Mail for Android In-Reply-To: References: <20210312113253.305040674@infradead.org> <20210312115749.065275711@infradead.org> <20B57BDC-9A3F-4B02-9BA9-41477088A6CE@zytor.com> <20240121195649.7355e1d5@rorschach.local.home> Message-ID: <4F17FAD6-9183-4F29-850D-8DE88FAB3658@zytor.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On January 21, 2024 5:17:36 PM PST, Thorsten Glaser wrote= : >Steven Rostedt dixit: > >>> >This was, incidentally, triggered by looking into a problem report th= at >>> >something did *not* work on a Geode LX system=2E >> >>What problem happened? > >It turned out to be a compiler issue (GCC thinks i686 means PPro, >not 686-class CPUs, and -fcf-protection causes long NOPs, which >not all 686-class CPUs support, to be inserted)=2E This turned out >to break a large part of Debian stable on OLPCs and other systems, >and the kernel=E2=80=99s changes in nopl handling were tabled as argument= s=2E > >https://www=2Ejookia=2Eorg/wiki/Nopl has a longer writeup on the nopl >history=2E > >bye, >//mirabilos i686 *is* Pentium Pro=2E=2E=2E