From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C934FC433F5 for ; Fri, 17 Dec 2021 15:01:09 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.248725.429021 (Exim 4.92) (envelope-from ) id 1myEj7-00023M-57; Fri, 17 Dec 2021 15:00:53 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 248725.429021; Fri, 17 Dec 2021 15:00:53 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1myEj7-00023F-26; Fri, 17 Dec 2021 15:00:53 +0000 Received: by outflank-mailman (input) for mailman id 248725; Fri, 17 Dec 2021 15:00:52 +0000 Received: from se1-gles-flk1-in.inumbo.com ([94.247.172.50] helo=se1-gles-flk1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1myEj6-000234-9R for xen-devel@lists.xenproject.org; Fri, 17 Dec 2021 15:00:52 +0000 Received: from ppsw-42.csi.cam.ac.uk (ppsw-42.csi.cam.ac.uk [131.111.8.142]) by se1-gles-flk1.inumbo.com (Halon) with ESMTPS id 1e2da664-5f4a-11ec-85d3-df6b77346a89; Fri, 17 Dec 2021 16:00:50 +0100 (CET) Received: from hades.srcf.societies.cam.ac.uk ([131.111.179.67]:43732) by ppsw-42.csi.cam.ac.uk (ppsw.cam.ac.uk [131.111.8.138]:25) with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) id 1myEiw-000AuQ-9Y (Exim 4.95) (return-path ); Fri, 17 Dec 2021 15:00:42 +0000 Received: from [192.168.1.10] (host-92-12-61-86.as13285.net [92.12.61.86]) (Authenticated sender: amc96) by hades.srcf.societies.cam.ac.uk (Postfix) with ESMTPSA id AF8921FD00; Fri, 17 Dec 2021 15:00:42 +0000 (GMT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 1e2da664-5f4a-11ec-85d3-df6b77346a89 X-Cam-AntiVirus: no malware found X-Cam-ScannerInfo: https://help.uis.cam.ac.uk/email-scanner-virus Message-ID: Date: Fri, 17 Dec 2021 15:00:42 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Content-Language: en-GB To: Jan Beulich , "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , George Dunlap , Wei Liu , Kevin Tian , Jun Nakajima , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= References: <57038a1c-671b-f0f9-1bf1-0ff9bae6e2dc@suse.com> From: Andrew Cooper Subject: Re: [PATCH 3/5] VMX: sync VM-exit perf counters with known VM-exit reasons In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 03/12/2021 12:05, Jan Beulich wrote: > --- a/xen/include/asm-x86/hvm/vmx/vmx.h > +++ b/xen/include/asm-x86/hvm/vmx/vmx.h > @@ -220,6 +220,8 @@ static inline void pi_clear_sn(struct pi > #define EXIT_REASON_XSAVES 63 > #define EXIT_REASON_XRSTORS 64 > > +#define EXIT_REASON_LAST EXIT_REASON_XRSTORS > + Given the problems with sentinals like this in the domctl/sysctl headers, I think this scheme would be less fragile if EXIT_REASON was an enum.  (Also, we seriously need to reduce the scope of these headers.  It's only just dawned on me why Intel uses EXIT_* and AMD uses VMEXIT_*) Alternatively, what about simply this:  #define EXIT_REASON_XSAVES              63  #define EXIT_REASON_XRSTORS             64 +/* Remember to update VMX_PERF_EXIT_REASON_SIZE too. */ ? This avoids having yet another sentinel in the mix, and will be visible in *every* patch review.  It also gets rid of the ifdefary in the vmexit handler. Another good move might be to have perfc_incra() have a printk_once() for out-of-range indices.  That way, people using perfcounters will have an easier time noticing if something is wrong. ~Andrew