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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4F9F5C0015E for ; Wed, 9 Aug 2023 15:11:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232596AbjHIPLF (ORCPT ); Wed, 9 Aug 2023 11:11:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35392 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231697AbjHIPLE (ORCPT ); Wed, 9 Aug 2023 11:11:04 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 107A5210A for ; Wed, 9 Aug 2023 08:11:02 -0700 (PDT) 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=1hWM8PckxVZy/FdzezlkIxwbHFx4HslYBKnPJIunZS8=; b=Qfw2MhHcBlBkBVhgxsxOEFeHCd eLwMgoFynvh+30KxpUt5u8WugznEhdtVjziXE/OWKHXOqk3CI8Uy4HAUZFa9Y/JQ37MT1wQhXp+Z6 WM/pWST4LhObQdS0TnhFadZ6lk5wbnRWhLLYYWd6pNnobSJ/FaQyZMC99AUuVmmDr2TPV6LjgbyT6 w0Sapma+mApl0C/zPIgF6/BX/wN61FanxD5XcNcKuSavUANcdIzOrEaztQJrgA+3aJvOnE0wmLHWn szGBBpMgI5VaEHtNffTYr2w+nEQckNvMZq/49dVy/vcShm1Qk/r1KKaCHfHqj2Lj35g+8ioCzhvcN FsDrwRhg==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1qTkpk-006rJt-Ib; Wed, 09 Aug 2023 15:10:48 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 0D7F330003A; Wed, 9 Aug 2023 17:10:48 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id E87932023C23F; Wed, 9 Aug 2023 17:10:47 +0200 (CEST) Date: Wed, 9 Aug 2023 17:10:47 +0200 From: Peter Zijlstra To: Josh Poimboeuf Cc: x86@kernel.org, linux-kernel@vger.kernel.org, David.Kaplan@amd.com, Andrew.Cooper3@citrix.com, gregkh@linuxfoundation.org Subject: Re: [RFC][PATCH 07/17] x86/cpu/kvm: Provide UNTRAIN_RET_VM Message-ID: <20230809151047.GT212435@hirez.programming.kicks-ass.net> References: <20230809071218.000335006@infradead.org> <20230809072200.922634286@infradead.org> <20230809135004.2xy76kqpptfqxsp5@treble> <20230809140644.GP212435@hirez.programming.kicks-ass.net> <20230809143000.tus4hqdaobk667eo@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230809143000.tus4hqdaobk667eo@treble> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 09, 2023 at 10:30:00AM -0400, Josh Poimboeuf wrote: > On Wed, Aug 09, 2023 at 04:06:44PM +0200, Peter Zijlstra wrote: > > On Wed, Aug 09, 2023 at 09:50:04AM -0400, Josh Poimboeuf wrote: > > > On Wed, Aug 09, 2023 at 09:12:25AM +0200, Peter Zijlstra wrote: > > > > With the difference being that UNTRAIN_RET_VM uses > > > > X86_FEATURE_IBPB_ON_VMEXIT instead of X86_FEATURE_ENTRY_IBPB. > > > > > > > > This cures VMEXIT doing potentially unret+IBPB or double IBPB. > > > > > > > > Signed-off-by: Peter Zijlstra (Intel) > > > > --- > > > > arch/x86/include/asm/nospec-branch.h | 11 +++++++++++ > > > > arch/x86/kernel/cpu/bugs.c | 17 ++++++++++++++++- > > > > arch/x86/kvm/svm/vmenter.S | 7 ++----- > > > > 3 files changed, 29 insertions(+), 6 deletions(-) > > > > > > > > --- a/arch/x86/include/asm/nospec-branch.h > > > > +++ b/arch/x86/include/asm/nospec-branch.h > > > > @@ -299,6 +299,17 @@ > > > > #endif > > > > .endm > > > > > > > > +.macro UNTRAIN_RET_VM > > > > +#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ > > > > + defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO) > > > > > > Maybe can be simplified? > > > > > > > See patches 9 and 10 :-) > > Can still be further simplified to CONFIG_RETHUNK? Hmm, probably, but my brain seems to be giving out. Let me do the whole dinner and kids to bed thing and I'll look again later.