From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 5DF1D23FC5A; Fri, 2 May 2025 11:08:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746184112; cv=none; b=e84RDTQKtOF7twRaQ6EasoYS3KSNtPWz8stPNXGi+MSOgD4uWWFvWw470PY0x1BamqEOirquPm2lfzCnSjp6cdLQNyPQYBAaKv4woPYrsqcj3lEUC5l7vfJ+V1E7PoCz3r4sqnuo0hzLusOplScHCtuXIdBjSdt7Ne5sxZiTZPg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746184112; c=relaxed/simple; bh=MTlzj5d2urKFEAV7iZYPY4R3fhJhN8yR0DXLHI6gP50=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bKdlvMW2JoydPvzq6yQHnYydcCsNcX9L0KgFSV1/63uYbTxGpW3VuSrwdlXmvzzOfONnArV+qQ1/aJIK+SIzgRPQxfI+JeSXDeQ0E/s1Vf5rUIL+mQmYEs+YrFXiB9ceM/ZwBOp8o2BX3Ixu5A3NR9YI9pK38AXtDBBpnkIGpHw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=kG8HmKNj; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none 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="kG8HmKNj" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=82slXiOoQVQC9//as6jdxQ6yG/Hw27pBqImDHueRTQc=; b=kG8HmKNjrK+7DQFDdc/MrJOMH4 Y0nlMW4CXIzpC7crHUmkOOlocJehtXtXKUzA4aVtzUGnerxozQrWEotMZUdXDJTuXRaX78tTyC70s 2ryexNLCNcJnWPOj6ZP004b3M5oGAdO3IPu6JGvMdusFAl1ZBD0NcLEo2wWAVoqOeHEDcQjQ+yqsv y5sqM4TbomGC2kUX+czUqgE/Zpth7Ud2EzoOi7MpYgqCPKambMTKgDVCC0fVDs8yIwJyP5qsr4Rci daVXRfSTj2jZ6a2qFppqYinMcJBjk0gIkRio2Jo5V5Xh03CnWDozNID5TuMgd7f+sQ8In2Dbhcue2 WSp0S2Dg==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.1 #2 (Red Hat Linux)) id 1uAoFe-0000000Endv-1amq; Fri, 02 May 2025 11:08:18 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 6F11730057C; Fri, 2 May 2025 13:08:17 +0200 (CEST) Date: Fri, 2 May 2025 13:08:17 +0200 From: Peter Zijlstra To: Paolo Bonzini Cc: x86@kernel.org, kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, seanjc@google.com, ardb@kernel.org, kees@kernel.org, Arnd Bergmann , gregkh@linuxfoundation.org, jpoimboe@kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-efi@vger.kernel.org, samitolvanen@google.com, ojeda@kernel.org Subject: Re: [PATCH v2 00/13] objtool: Detect and warn about indirect calls in __nocfi functions Message-ID: <20250502110817.GX4198@noisy.programming.kicks-ass.net> References: <20250430110734.392235199@infradead.org> 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-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Thu, May 01, 2025 at 08:33:57PM +0200, Paolo Bonzini wrote: > On Wed, Apr 30, 2025 at 1:26 PM Peter Zijlstra wrote: > > Notably the KVM fastop emulation stuff -- which I've completely rewritten for > > this version -- the generated code doesn't look horrific, but is slightly more > > verbose. I'm running on the assumption that instruction emulation is not super > > performance critical these days of zero VM-exit VMs etc. > > It's definitely going to be slower, but I guess it's okay these days. Yeah, it adds a bunch of branches at the very least. But that was indeed the argument, we shouldn't care much these days. > It's really only somewhat hot with really old processors > (pre-Westmere) and only when running big real mode code. Right, really old stuff :-)