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 9A2A0106FD98 for ; Fri, 13 Mar 2026 07:26:16 +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:Content-Type:MIME-Version: References:In-Reply-To:Subject:Cc:To:From:Message-ID: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=Vn2NaJwPk8Ly10EDcOLWqgZameb7xpgb5n9BBVBS9XM=; b=qXDZmO7TxI6+PwEoxkdXIfwoRp ylmb1Hpe4/NwY26KcaESvCzlzQYI3IwvvHDmh3PcY6b2MMOGN2qe7HDoof5zcvs9Ul/QOYry+J8Ga Vb+NW8b1w4z2xjCMdb1FTZIZfcUZUkgNBYTnSmPwbztXlABE37xfrNzBRI5HjNKLgby2/6PwCrrul raOpJxa5e8YwzWfiy2dxaVaRmDbxGbBxcUtq2I++vVfOyF1YNyBZ7H+uXFmKCNTR5iQvHT6ydbBwD IW6J/O907VNz/60rNTZaACSwDjjczyjLzkwu5z0Z9KmMPJaxfQzICdG5Mg+jakAe0VYEsASgc+sCs 2c/9CU3A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w0wuO-0000000H2qu-26D7; Fri, 13 Mar 2026 07:26:09 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1w0wuL-0000000H2qX-0BKv for linux-arm-kernel@lists.infradead.org; Fri, 13 Mar 2026 07:26:07 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 6EDFE43F22; Fri, 13 Mar 2026 07:26:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 405ADC19421; Fri, 13 Mar 2026 07:26:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773386764; bh=H7NGD0spNfXRA6FDcYy4akn4XYfi4m0ZEHlP6xHrrRc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=tW9WjjWGq5dTAyleJjchfB8yK7MEVcXCba8nP71TVwYVx11DXSTrvCVA2sL2vtkOE kklMXbsb5ksDX7KlaaMaeviV7K4OuAlIiZ5Csf3UGHqsxphfyuoksXXaCaxxFMJyTA THZ43v28T5lPxJ2Gx0vsY8oIUoBvjAH6XueAW7GqwPk4bs6e4BTkw+yW0gGlP6Tyhd 5oSfM0pE6G4ojfAwWlhWRaIkNf6mF7OxV2BHiHy/pV+ZsuQj7SmLAO1+D44sySwCrP rv/sR6lbmnGKckejFkS0fkUcr8v5wNlk3skkYRePpY12274EuyPn210OZSkwoQLKwx Cw+2Kbc58dYVQ== Received: from 82-132-235-41.dab.02.net ([82.132.235.41] helo=lobster-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1w0wuC-00000001Yti-3hld; Fri, 13 Mar 2026 07:25:57 +0000 Date: Fri, 13 Mar 2026 07:25:55 +0000 Message-ID: <87sea4chrw.wl-maz@kernel.org> From: Marc Zyngier To: Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, Catalin Marinas , Will Deacon , Oliver Upton , Mark Rutland , linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm64: Clear VTCR_EL2 in __init_el2_stage2() In-Reply-To: <20260313053857.1277828-1-anshuman.khandual@arm.com> References: <20260313053857.1277828-1-anshuman.khandual@arm.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 82.132.235.41 X-SA-Exim-Rcpt-To: anshuman.khandual@arm.com, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, oupton@kernel.org, mark.rutland@arm.com, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260313_002605_098357_E1A65ED8 X-CRM114-Status: GOOD ( 12.10 ) 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, 13 Mar 2026 05:38:57 +0000, Anshuman Khandual wrote: > > Clear VTCR_EL2 along with VTTBR_EL2 register in __init_el2_stage2(), which > ensures that MMU stage-2 translation remain disabled. Although clearing out > VTTBR_EL2 probably should have been sufficient but adding VTCR_EL2 improves > overall safety. This serves no purpose whatsoever. Even the write to VTTBR_EL2 is pointless, and writing 0 is no better than writing *any* other value. The only thing that matters at this stage is HCR_EL2.VM, which actually controls stage-2 translation (contrary to your above assertion). This of course is not captured by this macro. So what are you *really* trying to achieve? Thanks, M. -- Jazz isn't dead. It just smells funny.