From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A4B0B282F04 for ; Fri, 13 Mar 2026 07:26:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773386764; cv=none; b=ibAxx6bSENxzM1gBCZZ4woVggIxjP/rLanYjSc5h6D36Qhp/u90euG+ObPwU5DFM8RPLRT1J3NF98Txxb4rDMccu5Ud5jwxiozfUJG7kaLSUPQSJGVU0uCx3eFYkAanJLHZCi1xNBNQla84MlNQzAG+sJh9di9Tz9aNw+PYPL0s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773386764; c=relaxed/simple; bh=H7NGD0spNfXRA6FDcYy4akn4XYfi4m0ZEHlP6xHrrRc=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=ZuvdyUYPRlCaqAz7USjkpdMO1OxL6VcJFKhnvumgpjyReOmpnQJ0gNyfr/tUDVAzU0Ei6RUB6aewO+NLtuz6UKXUlflMqAti1a3VlocfnaX5T0WhrpBnzWa5ogpysQIBvuW/5QW303BYarCG+AUPS3dY6G70I6MPIWznGJ9T9TA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=tW9WjjWG; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="tW9WjjWG" 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) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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.