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 X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3D0DCC4708F for ; Fri, 4 Jun 2021 14:09:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 210A26140F for ; Fri, 4 Jun 2021 14:09:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230250AbhFDOLC (ORCPT ); Fri, 4 Jun 2021 10:11:02 -0400 Received: from foss.arm.com ([217.140.110.172]:39948 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230124AbhFDOLB (ORCPT ); Fri, 4 Jun 2021 10:11:01 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6678B2B; Fri, 4 Jun 2021 07:09:15 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [10.57.6.137]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4CE513F774; Fri, 4 Jun 2021 07:09:12 -0700 (PDT) Date: Fri, 4 Jun 2021 15:09:09 +0100 From: Mark Rutland To: Will Deacon Cc: kvmarm@lists.cs.columbia.edu, Marc Zyngier , James Morse , Alexandru Elisei , Suzuki K Poulose , Christoffer Dall , Paolo Bonzini , Fuad Tabba , Quentin Perret , Sean Christopherson , David Brazdil , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 2/4] KVM: arm64: Extend comment in has_vhe() Message-ID: <20210604140909.GB69333@C02TD0UTHF1T.local> References: <20210603183347.1695-1-will@kernel.org> <20210603183347.1695-3-will@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210603183347.1695-3-will@kernel.org> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Jun 03, 2021 at 07:33:45PM +0100, Will Deacon wrote: > has_vhe() expands to a compile-time constant when evaluated from the VHE > or nVHE code, alternatively checking a static key when called from > elsewhere in the kernel. On face value, this looks like a case of > premature optimization, but in fact this allows symbol references on > VHE-specific code paths to be dropped from the nVHE object. > > Expand the comment in has_vhe() to make this clearer, hopefully > discouraging anybody from simplifying the code. > > Cc: David Brazdil > Signed-off-by: Will Deacon Acked-by: Mark Rutland Mark. > --- > arch/arm64/include/asm/virt.h | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h > index 7379f35ae2c6..3218ca17f819 100644 > --- a/arch/arm64/include/asm/virt.h > +++ b/arch/arm64/include/asm/virt.h > @@ -111,6 +111,9 @@ static __always_inline bool has_vhe(void) > /* > * Code only run in VHE/NVHE hyp context can assume VHE is present or > * absent. Otherwise fall back to caps. > + * This allows the compiler to discard VHE-specific code from the > + * nVHE object, reducing the number of external symbol references > + * needed to link. > */ > if (is_vhe_hyp_code()) > return true; > -- > 2.32.0.rc0.204.g9fa02ecfa5-goog >