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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 75DDEC433EF for ; Mon, 15 Nov 2021 17:51:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 57CAD63407 for ; Mon, 15 Nov 2021 17:51:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237940AbhKORyY (ORCPT ); Mon, 15 Nov 2021 12:54:24 -0500 Received: from mail.kernel.org ([198.145.29.99]:50924 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237775AbhKORYD (ORCPT ); Mon, 15 Nov 2021 12:24:03 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 60CD46325A; Mon, 15 Nov 2021 17:17:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1636996626; bh=oyICd/a6c5ww8c1xKMkHgzV1Bv0FK8bubS6hzg/lM34=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=N4iJK83fmq8y9VjMCagoITxsyZ9Vz0/L+9MXPROt1SYj9TtWkvMigY3m46MgWZX3M twnxtGOs7stjogoLOfhNsjmhwBIyPMFgYLqc60Wol0Du7bCr51kvnt243dYRtDllbo 0MvNl9fUEPTVa5Qyv1lfrfc7+lyOvPIcGgrrC/Jw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Michael Kelley , Vitaly Kuznetsov , Wei Liu , Sasha Levin Subject: [PATCH 5.4 175/355] x86/hyperv: Protect set_hv_tscchange_cb() against getting preempted Date: Mon, 15 Nov 2021 18:01:39 +0100 Message-Id: <20211115165319.445996763@linuxfoundation.org> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211115165313.549179499@linuxfoundation.org> References: <20211115165313.549179499@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: Vitaly Kuznetsov [ Upstream commit 285f68afa8b20f752b0b7194d54980b5e0e27b75 ] The following issue is observed with CONFIG_DEBUG_PREEMPT when KVM loads: KVM: vmx: using Hyper-V Enlightened VMCS BUG: using smp_processor_id() in preemptible [00000000] code: systemd-udevd/488 caller is set_hv_tscchange_cb+0x16/0x80 CPU: 1 PID: 488 Comm: systemd-udevd Not tainted 5.15.0-rc5+ #396 Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.0 12/17/2019 Call Trace: dump_stack_lvl+0x6a/0x9a check_preemption_disabled+0xde/0xe0 ? kvm_gen_update_masterclock+0xd0/0xd0 [kvm] set_hv_tscchange_cb+0x16/0x80 kvm_arch_init+0x23f/0x290 [kvm] kvm_init+0x30/0x310 [kvm] vmx_init+0xaf/0x134 [kvm_intel] ... set_hv_tscchange_cb() can get preempted in between acquiring smp_processor_id() and writing to HV_X64_MSR_REENLIGHTENMENT_CONTROL. This is not an issue by itself: HV_X64_MSR_REENLIGHTENMENT_CONTROL is a partition-wide MSR and it doesn't matter which particular CPU will be used to receive reenlightenment notifications. The only real problem can (in theory) be observed if the CPU whose id was acquired with smp_processor_id() goes offline before we manage to write to the MSR, the logic in hv_cpu_die() won't be able to reassign it correctly. Reported-by: Michael Kelley Signed-off-by: Vitaly Kuznetsov Link: https://lore.kernel.org/r/20211012155005.1613352-1-vkuznets@redhat.com Signed-off-by: Wei Liu Signed-off-by: Sasha Levin --- arch/x86/hyperv/hv_init.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c index 79583bac9ac4a..812db1ac8cb11 100644 --- a/arch/x86/hyperv/hv_init.c +++ b/arch/x86/hyperv/hv_init.c @@ -155,7 +155,6 @@ void set_hv_tscchange_cb(void (*cb)(void)) struct hv_reenlightenment_control re_ctrl = { .vector = HYPERV_REENLIGHTENMENT_VECTOR, .enabled = 1, - .target_vp = hv_vp_index[smp_processor_id()] }; struct hv_tsc_emulation_control emu_ctrl = {.enabled = 1}; @@ -169,8 +168,12 @@ void set_hv_tscchange_cb(void (*cb)(void)) /* Make sure callback is registered before we write to MSRs */ wmb(); + re_ctrl.target_vp = hv_vp_index[get_cpu()]; + wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *((u64 *)&re_ctrl)); wrmsrl(HV_X64_MSR_TSC_EMULATION_CONTROL, *((u64 *)&emu_ctrl)); + + put_cpu(); } EXPORT_SYMBOL_GPL(set_hv_tscchange_cb); -- 2.33.0