From patchwork Mon Apr 14 12:40:56 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ben Horgan X-Patchwork-Id: 14050316 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 63BB5C369B5 for ; Mon, 14 Apr 2025 12:50:37 +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-Transfer-Encoding: MIME-Version:Message-ID:Date:Subject:Cc:To:From:Reply-To:Content-Type: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Owner; bh=Rm84iICJa/iwCuQG+A5PWWUm1CawJWiG/Ieu3PkXHnc=; b=mExJ5DJjFUM2AHplQqZ8I/0vMQ S2JtxeZxh0NYb2BwjtKr9QctQMQ1T9Evr3w67NPzyg2QFF9almpNf0v/h3gmAKqcjHEkNY9PuJ3gL nXMTtO79WBJH6PtcaRZoQtWNq8BOydR4da7HXlwlJkuAmQ2p1Y82NFuRdEua67AiHchfLycFXlBVT oWecPzKzDBN9GW3hl4uuvS9qlV0o2Qt3js4iL75jr/V3eQr1c+zyE4LY6pW5MTjzwSRT8gpeX/6NQ dk+Tw06891srkboG0VXEMkcwLGEMwDHp/y1OFeb1fJpeh456nK1ShVU7Ei20yO6e47z8gEsSunqbN TUxx6/nQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1u4JGd-000000020g7-33PT; Mon, 14 Apr 2025 12:50:27 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1u4J7x-00000001zNL-0CwG for linux-arm-kernel@lists.infradead.org; Mon, 14 Apr 2025 12:41:30 +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 0EB091007; Mon, 14 Apr 2025 05:41:25 -0700 (PDT) Received: from e134344.cambridge.arm.com (e134344.arm.com [10.1.196.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 91BAA3F59E; Mon, 14 Apr 2025 05:41:24 -0700 (PDT) From: Ben Horgan To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kselftest@vger.kernel.org Cc: maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, shuah@kernel.org, Ben Horgan Subject: [RFC PATCH 0/3] KVM: arm64: Don't claim MTE_ASYNC if not supported Date: Mon, 14 Apr 2025 13:40:56 +0100 Message-ID: <20250414124059.1938303-1-ben.horgan@arm.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250414_054129_135334_93BC9F2C X-CRM114-Status: UNSURE ( 7.91 ) X-CRM114-Notice: Please train this message. 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 The ID_AA64PFR1_EL1.MTE_frac field is currently hidden from KVM. However, when ID_AA64PFR1_EL1.MTE==2, ID_AA64PFR1_EL1.MTE_frac==0 indicates that MTE_ASYNC is supported. On a host with ID_AA64PFR1_EL1.MTE==2 but without MTE_ASYNC support a guest with the MTE capability enabled will incorrectly see MTE_ASYNC advertised as supported. This series fixes that. This was found by inspection and the current behaviour is not known to break anything. Linux doesn't check MTE_frac, and wrongly, assumes MTE async faults can be generated whenever MTE is supported. This is a separate problem and not addressed here. I am looking for feedback on whether this change is valuable or otherwise. Ben Horgan (3): arm64/sysreg: Expose MTE_frac so that it is visible to KVM KVM: arm64: Make MTE_frac masking conditional on MTE capability KVM: selftests: Confirm exposing MTE_frac does not break migration arch/arm64/kernel/cpufeature.c | 1 + arch/arm64/kvm/sys_regs.c | 26 ++++++- .../testing/selftests/kvm/arm64/set_id_regs.c | 77 ++++++++++++++++++- 3 files changed, 101 insertions(+), 3 deletions(-) base-commit: 8ffd015db85fea3e15a77027fda6c02ced4d2444