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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 44DAEC4332B for ; Fri, 15 Jan 2021 13:02:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 120152313E for ; Fri, 15 Jan 2021 13:02:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732989AbhAOMcg (ORCPT ); Fri, 15 Jan 2021 07:32:36 -0500 Received: from mail.kernel.org ([198.145.29.99]:39144 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732970AbhAOMcc (ORCPT ); Fri, 15 Jan 2021 07:32:32 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7D1AF23370; Fri, 15 Jan 2021 12:31:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1610713911; bh=Dt8vvzvb3KqJE72tEHare2drQPOaOXOvXKCrvsFGocI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BkfdE74D/kZ13K+ATlj9i6JNvyVMKqMPgk8v8DwjnBsReLbxV5HL/XIxZstgmacdE 5EDSgqIHYhrdFQGhqzr65/VB8dTlxvxbszqgGPx5LY4tBl9VoYtBgvVFZwq0NTtw8g zxJ5bQcBNBJe5lVh/kNc5mcRWXqEG2JCFO/vFzV0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexandru Elisei , Marc Zyngier Subject: [PATCH 4.14 26/28] KVM: arm64: Dont access PMCR_EL0 when no PMU is available Date: Fri, 15 Jan 2021 13:28:03 +0100 Message-Id: <20210115121958.058017373@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210115121956.731354372@linuxfoundation.org> References: <20210115121956.731354372@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Marc Zyngier commit 2a5f1b67ec577fb1544b563086e0377f095f88e2 upstream. We reset the guest's view of PMCR_EL0 unconditionally, based on the host's view of this register. It is however legal for an implementation not to provide any PMU, resulting in an UNDEF. The obvious fix is to skip the reset of this shadow register when no PMU is available, sidestepping the issue entirely. If no PMU is available, the guest is not able to request a virtual PMU anyway, so not doing nothing is the right thing to do! It is unlikely that this bug can hit any HW implementation though, as they all provide a PMU. It has been found using nested virt with the host KVM not implementing the PMU itself. Fixes: ab9468340d2bc ("arm64: KVM: Add access handler for PMCR register") Reviewed-by: Alexandru Elisei Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20201210083059.1277162-1-maz@kernel.org Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kvm/sys_regs.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -470,6 +470,10 @@ static void reset_pmcr(struct kvm_vcpu * { u64 pmcr, val; + /* No PMU available, PMCR_EL0 may UNDEF... */ + if (!kvm_arm_support_pmu_v3()) + return; + pmcr = read_sysreg(pmcr_el0); /* * Writable bits of PMCR_EL0 (ARMV8_PMU_PMCR_MASK) are reset to UNKNOWN