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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 CD85EC433E1 for ; Mon, 6 Jul 2020 11:05:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AC9502075B for ; Mon, 6 Jul 2020 11:05:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594033536; bh=pNwXVAMDXVJlIpm6TO8om9y6iGboItUmVHhsv43zIi0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=mrHMpTcxm2v0SvTDsYLAQwi7gluZBQ83alrAOvdezoD2cfMysS68FsA0yt0NMklGR O7TEg6hr2C4uQu1WKP2TMNZMvL3A4SpnGnazd+6TGNs6LG7LqlNVzcFtKuREz3XijH uZQyS8ryF/hdnZIg71RjJc3DGYNmHDoebQ4enlcc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728878AbgGFLFf (ORCPT ); Mon, 6 Jul 2020 07:05:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:57690 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728697AbgGFLFf (ORCPT ); Mon, 6 Jul 2020 07:05:35 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 767952073E; Mon, 6 Jul 2020 11:05:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594033534; bh=pNwXVAMDXVJlIpm6TO8om9y6iGboItUmVHhsv43zIi0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YbQDW/lcnduuDKC8kaeWjsU5cTyH+Qwz4b/f+LWIOMadaiDAfbAp4ayIwKyy1YEF+ QdSct6GVOwoeY4bmBgshAH0xCERJ6xxWC9IYm8v54KK1OtR9PX4iDw/PRh1zCf2ffZ 6yCXO9WnwIVZ6AOCNmbzMAnSc44UxpbkSrkZ/zXM= Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=why.lan) by disco-boy.misterjones.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1jsOwG-009Qgb-UX; Mon, 06 Jul 2020 12:05:33 +0100 From: Marc Zyngier To: Paolo Bonzini Cc: Andrew Scull , Andrew Murray , James Morse , Julien Thierry , Suzuki K Poulose , kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: [PATCH 1/2] KVM: arm64: PMU: Fix per-CPU access in preemptible context Date: Mon, 6 Jul 2020 12:05:20 +0100 Message-Id: <20200706110521.1615794-2-maz@kernel.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200706110521.1615794-1-maz@kernel.org> References: <20200706110521.1615794-1-maz@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: pbonzini@redhat.com, ascull@google.com, amurray@thegoodpenguin.co.uk, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Commit 07da1ffaa137 ("KVM: arm64: Remove host_cpu_context member from vcpu structure") has, by removing the host CPU context pointer, exposed that kvm_vcpu_pmu_restore_guest is called in preemptible contexts: [ 266.932442] BUG: using smp_processor_id() in preemptible [00000000] code: qemu-system-aar/779 [ 266.939721] caller is debug_smp_processor_id+0x20/0x30 [ 266.944157] CPU: 2 PID: 779 Comm: qemu-system-aar Tainted: G E 5.8.0-rc3-00015-g8d4aa58b2fe3 #1374 [ 266.954268] Hardware name: amlogic w400/w400, BIOS 2020.04 05/22/2020 [ 266.960640] Call trace: [ 266.963064] dump_backtrace+0x0/0x1e0 [ 266.966679] show_stack+0x20/0x30 [ 266.969959] dump_stack+0xe4/0x154 [ 266.973338] check_preemption_disabled+0xf8/0x108 [ 266.977978] debug_smp_processor_id+0x20/0x30 [ 266.982307] kvm_vcpu_pmu_restore_guest+0x2c/0x68 [ 266.986949] access_pmcr+0xf8/0x128 [ 266.990399] perform_access+0x8c/0x250 [ 266.994108] kvm_handle_sys_reg+0x10c/0x2f8 [ 266.998247] handle_exit+0x78/0x200 [ 267.001697] kvm_arch_vcpu_ioctl_run+0x2ac/0xab8 Note that the bug was always there, it is only the switch to using percpu accessors that made it obvious. The fix is to wrap these accesses in a preempt-disabled section, so that we sample a coherent context on trap from the guest. Fixes: 435e53fb5e21 ("arm64: KVM: Enable VHE support for :G/:H perf event modifiers") Cc:: Andrew Murray Signed-off-by: Marc Zyngier --- arch/arm64/kvm/pmu.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/pmu.c b/arch/arm64/kvm/pmu.c index b5ae3a5d509e..3c224162b3dd 100644 --- a/arch/arm64/kvm/pmu.c +++ b/arch/arm64/kvm/pmu.c @@ -159,7 +159,10 @@ static void kvm_vcpu_pmu_disable_el0(unsigned long events) } /* - * On VHE ensure that only guest events have EL0 counting enabled + * On VHE ensure that only guest events have EL0 counting enabled. + * This is called from both vcpu_{load,put} and the sysreg handling. + * Since the latter is preemptible, special care must be taken to + * disable preemption. */ void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu) { @@ -169,12 +172,14 @@ void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu) if (!has_vhe()) return; + preempt_disable(); host = this_cpu_ptr(&kvm_host_data); events_guest = host->pmu_events.events_guest; events_host = host->pmu_events.events_host; kvm_vcpu_pmu_enable_el0(events_guest); kvm_vcpu_pmu_disable_el0(events_host); + preempt_enable(); } /* -- 2.27.0