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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=unavailable 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 20033C47095 for ; Mon, 7 Jun 2021 18:49:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 00358610A1 for ; Mon, 7 Jun 2021 18:49:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231200AbhFGSuz (ORCPT ); Mon, 7 Jun 2021 14:50:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:55374 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230316AbhFGSuy (ORCPT ); Mon, 7 Jun 2021 14:50:54 -0400 Received: from oasis.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (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 B47996108C; Mon, 7 Jun 2021 18:49:01 +0000 (UTC) Date: Mon, 7 Jun 2021 14:48:45 -0400 From: Steven Rostedt To: Sean Christopherson Cc: Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: x86: Ensure liveliness of nested VM-Enter fail tracepoint message Message-ID: <20210607144845.74a893d6@oasis.local.home> In-Reply-To: <20210607175748.674002-1-seanjc@google.com> References: <20210607175748.674002-1-seanjc@google.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 7 Jun 2021 10:57:48 -0700 Sean Christopherson wrote: > Use the __string() machinery provided by the tracing subystem to make a > copy of the string literals consumed by the "nested VM-Enter failed" > tracepoint. A complete copy is necessary to ensure that the tracepoint > can't outlive the data/memory it consumes and deference stale memory. > > Because the tracepoint itself is defined by kvm, if kvm-intel and/or > kvm-amd are built as modules, the memory holding the string literals > defined by the vendor modules will be freed when the module is unloaded, > whereas the tracepoint and its data in the ring buffer will live until > kvm is unloaded (or "indefinitely" if kvm is built-in). > > This bug has existed since the tracepoint was added, but was recently > exposed by a new check in tracing to detect exactly this type of bug. > > fmt: '%s%s > ' current_buffer: ' vmx_dirty_log_t-140127 [003] .... kvm_nested_vmenter_failed: ' > WARNING: CPU: 3 PID: 140134 at kernel/trace/trace.c:3759 trace_check_vprintf+0x3be/0x3e0 > CPU: 3 PID: 140134 Comm: less Not tainted 5.13.0-rc1-ce2e73ce600a-req #184 > Hardware name: ASUS Q87M-E/Q87M-E, BIOS 1102 03/03/2014 > RIP: 0010:trace_check_vprintf+0x3be/0x3e0 > Code: <0f> 0b 44 8b 4c 24 1c e9 a9 fe ff ff c6 44 02 ff 00 49 8b 97 b0 20 > RSP: 0018:ffffa895cc37bcb0 EFLAGS: 00010282 > RAX: 0000000000000000 RBX: ffffa895cc37bd08 RCX: 0000000000000027 > RDX: 0000000000000027 RSI: 00000000ffffdfff RDI: ffff9766cfad74f8 > RBP: ffffffffc0a041d4 R08: ffff9766cfad74f0 R09: ffffa895cc37bad8 > R10: 0000000000000001 R11: 0000000000000001 R12: ffffffffc0a041d4 > R13: ffffffffc0f4dba8 R14: 0000000000000000 R15: ffff976409f2c000 > FS: 00007f92fa200740(0000) GS:ffff9766cfac0000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000559bd11b0000 CR3: 000000019fbaa002 CR4: 00000000001726e0 > Call Trace: > trace_event_printf+0x5e/0x80 > trace_raw_output_kvm_nested_vmenter_failed+0x3a/0x60 [kvm] > print_trace_line+0x1dd/0x4e0 > s_show+0x45/0x150 > seq_read_iter+0x2d5/0x4c0 > seq_read+0x106/0x150 > vfs_read+0x98/0x180 > ksys_read+0x5f/0xe0 > do_syscall_64+0x40/0xb0 > entry_SYSCALL_64_after_hwframe+0x44/0xae > > Cc: Steven Rostedt > Fixes: 380e0055bc7e ("KVM: nVMX: trace nested VM-Enter failures detected by H/W") > Signed-off-by: Sean Christopherson > --- > Reviewed-by: Steven Rostedt (VMware) -- Steve