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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B2FA8C433F5 for ; Mon, 4 Oct 2021 12:12:48 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2A40361181 for ; Mon, 4 Oct 2021 12:12:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 2A40361181 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:44142 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mXMpr-00089l-Dk for qemu-devel@archiver.kernel.org; Mon, 04 Oct 2021 08:12:47 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:44182) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mXMgY-0001w3-F6 for qemu-devel@nongnu.org; Mon, 04 Oct 2021 08:03:10 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:50135) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mXMgV-0006Nh-Jk for qemu-devel@nongnu.org; Mon, 04 Oct 2021 08:03:10 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1633348987; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5OgDf6BrqOXrYlJwSdM6+2Enyt2bTUEUbFrjj4pWhyM=; b=Wl3S6OtSBbKoWbIsN0NgTPSE4jFpsryPwdkjYCaaRSjkD625/SYOctcB3qqLu5WKys8djV EMoDHLmFGq4ANWC3ayPLsV/5+osfT9WR8J46bajKlATO/NQH37N/4eiyBFCjKI6aQjr0YO eaHy5W7qVVHkM/dcF3Zk4tOhwa8n3W4= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-297-OHvYf5mqMtanAssbt2L5Ow-1; Mon, 04 Oct 2021 08:03:06 -0400 X-MC-Unique: OHvYf5mqMtanAssbt2L5Ow-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9C0D381426F; Mon, 4 Oct 2021 12:03:01 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.194.159]) by smtp.corp.redhat.com (Postfix) with ESMTP id 692CF19C59; Mon, 4 Oct 2021 12:02:58 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Subject: [PATCH v4 7/7] util/oslib-posix: Forward SIGBUS to MCE handler under Linux Date: Mon, 4 Oct 2021 14:02:08 +0200 Message-Id: <20211004120208.7409-8-david@redhat.com> In-Reply-To: <20211004120208.7409-1-david@redhat.com> References: <20211004120208.7409-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.066, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Pankaj Gupta , =?UTF-8?q?Daniel=20P=20=2E=20Berrang=C3=A9?= , Eduardo Habkost , "Michael S. Tsirkin" , David Hildenbrand , "Dr . David Alan Gilbert" , Igor Mammedov , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Temporarily modifying the SIGBUS handler is really nasty, as we might be unlucky and receive an MCE SIGBUS while having our handler registered. Unfortunately, there is no way around messing with SIGBUS when MADV_POPULATE_WRITE is not applicable or not around. Let's forward SIGBUS that don't belong to us to the already registered handler and document the situation. Reviewed-by: Daniel P. Berrangé Signed-off-by: David Hildenbrand --- softmmu/cpus.c | 4 ++++ util/oslib-posix.c | 36 +++++++++++++++++++++++++++++++++--- 2 files changed, 37 insertions(+), 3 deletions(-) diff --git a/softmmu/cpus.c b/softmmu/cpus.c index 071085f840..23bca46b07 100644 --- a/softmmu/cpus.c +++ b/softmmu/cpus.c @@ -352,6 +352,10 @@ static void qemu_init_sigbus(void) { struct sigaction action; + /* + * ALERT: when modifying this, take care that SIGBUS forwarding in + * os_mem_prealloc() will continue working as expected. + */ memset(&action, 0, sizeof(action)); action.sa_flags = SA_SIGINFO; action.sa_sigaction = sigbus_handler; diff --git a/util/oslib-posix.c b/util/oslib-posix.c index 9829149e4b..5c47aa9cb7 100644 --- a/util/oslib-posix.c +++ b/util/oslib-posix.c @@ -95,6 +95,7 @@ typedef struct MemsetThread MemsetThread; /* used by sigbus_handler() */ static MemsetContext *sigbus_memset_context; +struct sigaction sigbus_oldact; static QemuMutex sigbus_mutex; static QemuMutex page_mutex; @@ -446,7 +447,11 @@ const char *qemu_get_exec_dir(void) return exec_dir; } +#ifdef CONFIG_LINUX +static void sigbus_handler(int signal, siginfo_t *siginfo, void *ctx) +#else /* CONFIG_LINUX */ static void sigbus_handler(int signal) +#endif /* CONFIG_LINUX */ { int i; @@ -459,6 +464,26 @@ static void sigbus_handler(int signal) } } } + +#ifdef CONFIG_LINUX + /* + * We assume that the MCE SIGBUS handler could have been registered. We + * should never receive BUS_MCEERR_AO on any of our threads, but only on + * the main thread registered for PR_MCE_KILL_EARLY. Further, we should not + * receive BUS_MCEERR_AR triggered by action of other threads on one of + * our threads. So, no need to check for unrelated SIGBUS when seeing one + * for our threads. + * + * We will forward to the MCE handler, which will either handle the SIGBUS + * or reinstall the default SIGBUS handler and reraise the SIGBUS. The + * default SIGBUS handler will crash the process, so we don't care. + */ + if (sigbus_oldact.sa_flags & SA_SIGINFO) { + sigbus_oldact.sa_sigaction(signal, siginfo, ctx); + return; + } +#endif /* CONFIG_LINUX */ + warn_report("os_mem_prealloc: unrelated SIGBUS detected and ignored"); } static void *do_touch_pages(void *arg) @@ -628,10 +653,10 @@ void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus, { static gsize initialized; int ret; - struct sigaction act, oldact; size_t hpagesize = qemu_fd_getpagesize(fd); size_t numpages = DIV_ROUND_UP(memory, hpagesize); bool use_madv_populate_write; + struct sigaction act; /* * Sense on every invocation, as MADV_POPULATE_WRITE cannot be used for @@ -647,10 +672,15 @@ void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus, qemu_mutex_lock(&sigbus_mutex); memset(&act, 0, sizeof(act)); +#ifdef CONFIG_LINUX + act.sa_sigaction = &sigbus_handler; + act.sa_flags = SA_SIGINFO; +#else /* CONFIG_LINUX */ act.sa_handler = &sigbus_handler; act.sa_flags = 0; +#endif /* CONFIG_LINUX */ - ret = sigaction(SIGBUS, &act, &oldact); + ret = sigaction(SIGBUS, &act, &sigbus_oldact); if (ret) { error_setg_errno(errp, errno, "os_mem_prealloc: failed to install signal handler"); @@ -667,7 +697,7 @@ void os_mem_prealloc(int fd, char *area, size_t memory, int smp_cpus, } if (!use_madv_populate_write) { - ret = sigaction(SIGBUS, &oldact, NULL); + ret = sigaction(SIGBUS, &sigbus_oldact, NULL); if (ret) { /* Terminate QEMU since it can't recover from error */ perror("os_mem_prealloc: failed to reinstall signal handler"); -- 2.31.1