Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752164AbaLET6I (ORCPT ); Fri, 5 Dec 2014 14:58:08 -0500 Received: from mail-la0-f46.google.com ([209.85.215.46]:57977 "EHLO mail-la0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751398AbaLET6G (ORCPT ); Fri, 5 Dec 2014 14:58:06 -0500 MIME-Version: 1.0 In-Reply-To: <1417774227.2232.1.camel@linaro.org> References: <1417671172-52915-1-git-send-email-wangnan0@huawei.com> <1417671360-53399-1-git-send-email-wangnan0@huawei.com> <1417710073.2239.10.camel@linaro.org> <5481289E.4060504@huawei.com> <1417774227.2232.1.camel@linaro.org> From: Peter Maydell Date: Fri, 5 Dec 2014 19:57:43 +0000 Message-ID: Subject: Re: [PATCH v12 7/7] ARM: kprobes: enable OPTPROBES for ARM 32 To: "Jon Medhurst (Tixy)" Cc: Wang Nan , masami.hiramatsu.pt@hitachi.com, lizefan@huawei.com, Russell King , lkml - Kernel Mailing List , arm-mail-list Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5 December 2014 at 10:10, Jon Medhurst (Tixy) wrote: > I don't know much about QEMU and have never used it, but I'm assuming > QEMU doesn't make any attempt to simulate caches like the data cache, > instruction cache, TLBs, branch predictor? Does it even emulate multiple > CPUs with multiple host CPU threads? Basically, I very much doubt QEMU > is a very good test of kernel code in general, and especially code that > modifies code and has multiple cpus running in parallel. You're generally correct here, yes. QEMU doesn't emulate caches or TLBs or branch predictors, and we currently emulate SMP by doing round-robin execution on a single host thread (though we're working on that for performance reasons). There are also a range of buggy-guest-code conditions (alignment faults, for instance) which we don't emulate. I tend to think of QEMU's overall philosophy as "run known-good code quickly" rather than "diagnose problems in buggy code". So it's definitely wise to test complicated kernel code like this on real hardware (though of course QEMU may be very helpful in speeding up the development cycle compared to h/w). thanks -- PMM -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/