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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 E99D3C19776 for ; Fri, 28 Feb 2025 10:18:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=H5ef1Hym6aX0nRxhyO5CK3F0Qiblx/gteQztPbQDklo=; b=VCa1ZVFkknZ4Hs5/NWWeIS6Ovv rwQ4Tq/E+gsGNJ5Ykspn8DvE1/vDTyvcxbdfzlo0z73px/wWR/EJ/RJXQIK1IqG7uZ7BOlLg4//8W CETcjH8qpYTe9T00nQxtcDWUrtKIgPeFXF+zE7ZHxvtHU3wjYu/v2f69g/saRI0BNzxMBPGR5Gsj7 7DGoJHPYOIw3dcF24SdEkxvGqhZKPYNF3rsOlfCnIxZ7KjVDhzJzeL1+LoUmqgW3b9tmaG2pWLAXE GKs/43pOjEZ9Dy22Gepu392j0+1w2Lk1ZUPp9gBQwk9rZTZynX1hPFJZDHx3gtZlJCNcCS2AiSKFv ZYOm31Nw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tnxRs-0000000AYyy-4AMK; Fri, 28 Feb 2025 10:18:28 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tnxNp-0000000AXZw-0Kb1 for linux-arm-kernel@lists.infradead.org; Fri, 28 Feb 2025 10:14:18 +0000 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 9C51D1688; Fri, 28 Feb 2025 02:14:31 -0800 (PST) Received: from localhost (e132581.arm.com [10.2.76.71]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F29493F6A8; Fri, 28 Feb 2025 02:14:15 -0800 (PST) Date: Fri, 28 Feb 2025 10:14:11 +0000 From: Leo Yan To: Marc Zyngier Cc: Mark Rutland , linux-arm-kernel@lists.infradead.org, ahmed.genidi@arm.com, ben.horgan@arm.com, catalin.marinas@arm.com, kvmarm@lists.linux.dev, oliver.upton@linux.dev, will@kernel.org Subject: Re: [PATCH 1/2] KVM: arm64: Initialize HCR_EL2.E2H early Message-ID: <20250228101411.GE2157064@e132581.arm.com> References: <20250227180526.1204723-1-mark.rutland@arm.com> <20250227180526.1204723-2-mark.rutland@arm.com> <20250228092955.GC2157064@e132581.arm.com> <86y0xqpfpj.wl-maz@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <86y0xqpfpj.wl-maz@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250228_021417_164999_38D60392 X-CRM114-Status: GOOD ( 25.57 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Feb 28, 2025 at 09:43:20AM +0000, Marc Zyngier wrote: [...] > On Fri, 28 Feb 2025 09:29:55 +0000, > Leo Yan wrote: > > > > Hi Mark, > > > > On Thu, Feb 27, 2025 at 06:05:25PM +0000, Mark Rutland wrote: > > > > [...] > > > > > +.macro init_el2_hcr val > > > + mov_q x0, \val > > > + > > > + /* > > > + * Compliant CPUs advertise their VHE-onlyness with > > > + * ID_AA64MMFR4_EL1.E2H0 < 0. On such CPUs HCR_EL2.E2H is RES1, but it > > > + * can reset into an UNKNOWN state and might not read as 1 until it has > > > + * been initialized explicitly. > > > > For ID_AA64MMFR4_EL1.E2H0 < 0 case, the code actually clears the > > HCR_EL2.E2H bit. > > > > Hence, the comment should be corrected as: "... it can reset into an > > UNKNOWN state and might not read as 0 until it has been initialized > > explicitly". > > The comment is just fine. It is the code that is wrong, as it avoids > setting E2H when E2H0 < 0 while we want the exact opposite behaviour. > > As a result, 'b.lt' really should be a 'b.ge'. Or the original code > kept as is. Thanks for correcting. > > > + * > > > + * Fruity CPUs seem to have HCR_EL2.E2H set to RAO/WI, but > > > + * don't advertise it (they predate this relaxation). > > > + * > > > + * Initalize HCR_EL2.E2H so that later code can rely upon HCR_EL2.E2H > > > + * indicating whether the CPU is running in E2H mode. > > > + */ > > > > I think it is even better to clear the HCR_E2H bit first. This can > > avoid any dependency on the passed parameter 'val'. > > What are you trying to avoid? A random value passed as a parameter to > the macro? Yes, an unexpected value passed to the macro is a concern. If the intentaion here is only to set the HCR_EL2.E2H bit when E2H0 < 0, we don't need to cosndier other configurations and current code is just fine? Thanks, Leo