From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B7706372B28 for ; Fri, 19 Jun 2026 11:18:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781867939; cv=none; b=ufQIPPe9Fs4KfnJZoVJxtlMJwmFnZlVkM061pHFy/ZCYY5lATpahneIHFV3gryxHZTGj6VfK/EupTW6qne2OOK3NE3UYH6pDTSGDmTUn0o1wlHuVbQ7elbmbC5rzY75j2IlKMqPXeHcLzYbvMyIQuIrJM6wLZj+ZW2wUksnnhp8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781867939; c=relaxed/simple; bh=WM7+aeFUbK3RXRUHJ8jUyr/1nH6Uo4e1aiXWp36zbkc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fLtQ7wMsncM20mVAFeitDdOaY89b7U6nNmwfV7GYEIqL6rCT/1t2K+cQbxCgZAz7M3GsDgvUWw2wDFN4DzwC++INDh7MVovjlvxmR9IepuJHUOK0pMEkk6SgS/eRCGaoQTXEWz5co8enzthdRTJWIM1hePuKyIjCyDZthQlKvk8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=i10d1Ln9; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="i10d1Ln9" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Tlh8JBCvKEi3yQcMFD7m34xU4f1/PZw+2dtDn7cMY48=; b=i10d1Ln9rP1DGBDMsjOHJuS7y8 7lfQcLqcQBLxHO127RsdcuOI88COsSIFR/ww9b98+EowanRjRuFolRRQMy5fmVHVq/pqcz0/u7cTd AUoVqmJmxUhZgG/tCS4yVFBP0yhAdpI2WE5y1BWdRJNgj1RM1zZBiAzepcSNbaJr7V+k0fwnPZMYw Ak9c2Bpnk0bd1dqiiJioYdEwNdGpkISLfrTssiqKjLWcYAmqI3ynEeHCsmSJsw1aRBwVKMINex6nY rflwOY9PnxuL6bjAbBBOovODgcsElKyKP749RfuaBx12pkzb4sJ6GjAi6OV0ZPl6CH2+52IYVQgi7 CMw0fmBw==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1waXFJ-0000000G7qs-2LfJ; Fri, 19 Jun 2026 11:18:50 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id EDADC300578; Fri, 19 Jun 2026 13:18:48 +0200 (CEST) Date: Fri, 19 Jun 2026 13:18:48 +0200 From: Peter Zijlstra To: "H. Peter Anvin" Cc: Linus Torvalds , tglx@kernel.org, mingo@redhat.com, bp@alien8.de, Nathan Chancellor , Calvin Owens , Dave Hansen , x86-ML , LKML Subject: Re: 8aeb879baf12 - significant system call latency regression, bisected Message-ID: <20260619111848.GO42921@noisy.programming.kicks-ass.net> References: <20260613085919.GF42921@noisy.programming.kicks-ass.net> <203E61B7-290F-4F87-860F-B352D0072703@zytor.com> <20260616082814.GQ48970@noisy.programming.kicks-ass.net> <20260617123718.GM49951@noisy.programming.kicks-ass.net> <20260619081427.GD49529@noisy.programming.kicks-ass.net> <6B52EE70-FB51-4053-B888-DD3EC6D66C54@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=us-ascii Content-Disposition: inline In-Reply-To: <6B52EE70-FB51-4053-B888-DD3EC6D66C54@zytor.com> On Fri, Jun 19, 2026 at 03:23:52AM -0700, H. Peter Anvin wrote: > On June 19, 2026 1:14:27 AM PDT, Peter Zijlstra wrote: > >On Wed, Jun 17, 2026 at 02:37:18PM +0200, Peter Zijlstra wrote: > >> - makes -fno-jump-tables unconditional > >> - removes array_index_nospec() from the syscall dispatch > > > >FWIW, this also allows making all SYSCALLs __noendbr, very much > >including the 'legacy' sys_call_table :-) > > > >Compile tested with IA32_EMULATION=n and reliably yields: > > > >vmlinux.o: warning: objtool: sys_call_table+0x0: data relocation to !ENDBR: __x64_sys_read+0x0 > >... > >vmlinux.o: warning: objtool: sys_call_table+0xeb0: data relocation to !ENDBR: __x64_sys_listns+0x0 > > > >(which is just one little objtool patch away from being fixed) > > > >and boots fine (in kvm). > *Very* nice indeed. > > I was definitely hoping this would be the next step. A few patches here: git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git x86/syscall That now includes IA32_EMULATION and a few terse changelogs. The alignment thing went missing since that didn't seem to be very good.