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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 27323C7618B for ; Fri, 26 Jul 2019 13:53:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0B46822CE8 for ; Fri, 26 Jul 2019 13:53:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388893AbfGZNxM (ORCPT ); Fri, 26 Jul 2019 09:53:12 -0400 Received: from mail-qt1-f196.google.com ([209.85.160.196]:34302 "EHLO mail-qt1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388284AbfGZNxF (ORCPT ); Fri, 26 Jul 2019 09:53:05 -0400 Received: by mail-qt1-f196.google.com with SMTP id k10so52705493qtq.1 for ; Fri, 26 Jul 2019 06:53:05 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=AG8g0/5+Esm5c3gfwUTGC7xBT2DUyGJWbBLEtSQE6Lo=; b=AtLhvXnrKCs8lMYMnz9aOAFh2heSHPwNUOPeZ8tQfpI29K8JAUWNKh44ISm9RlKSMP mxR4ml8DfgYJLCrPSEQ9l732QeVgfikXIGzRVY8pcJDGYDhOc/MiuNnVSh/yLFrGe6Tn fbtGnviDZVGnFREHGyg/9olhXMA/8ZpTOMIZsgVly28j+JOd3hShcQ6PLvN7I64y9E7P PxVqAtBO6GOcjtDKcJaKht7UEl1j9FyqeL/9kWf8sIzJRA+r3Jf7VS08w6HWMq3/rSzB JqOGaYDB5cJwN8VVjqDH7bbKjSIIDmfk+mbctJOA/HhVKr/VVWJHsfGa3LLWpOBWWgSg M29A== X-Gm-Message-State: APjAAAX746WL7JNW7QYf5DygxC/xiP8/RmaCs1rUv2weUhmPo9ziSzaK KtOGv5bDVdpBZcwUuBunzgNjt/Y/kkHVGA== X-Google-Smtp-Source: APXvYqydwEkRiDUhjkzyGjQfoaMf8JbYOCxKxauTFB3YoeZG49kK7ARiVn02SSH3ZF9H39y3z1BKaA== X-Received: by 2002:a0c:b521:: with SMTP id d33mr68309462qve.239.1564149185035; Fri, 26 Jul 2019 06:53:05 -0700 (PDT) Received: from redhat.com ([212.92.104.165]) by smtp.gmail.com with ESMTPSA id v17sm30156688qtc.23.2019.07.26.06.53.02 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Fri, 26 Jul 2019 06:53:04 -0700 (PDT) Date: Fri, 26 Jul 2019 09:52:59 -0400 From: "Michael S. Tsirkin" To: Jason Wang Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org Subject: Re: [PATCH] vhost: disable metadata prefetch optimization Message-ID: <20190726095044-mutt-send-email-mst@kernel.org> References: <20190726115021.7319-1-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Jul 26, 2019 at 07:57:25PM +0800, Jason Wang wrote: > > On 2019/7/26 下午7:51, Michael S. Tsirkin wrote: > > This seems to cause guest and host memory corruption. > > Disable for now until we get a better handle on that. > > > > Signed-off-by: Michael S. Tsirkin > > --- > > > > I put this in linux-next, we'll re-enable if we can fix > > the outstanding issues in a short order. > > > Btw, is this more suitable to e.g revert the > 842aa64eddacd23adc6ecdbc69cb2030bec47122 Yes I did that too. > and let syzbot fuzz more on the > current code? Current metadata direct access code is known to corrupt guest and host memory - I don't feel we need more fuzzing. > > I think we won't accept that patch eventually, so I suspect what syzbot > reports today is a false positives. Today's reports are real, it's a bug in my patch. But I reverted it - the below is an easier way to make sure at least linux-next is stable for everyone. > > Thanks > > > > > > drivers/vhost/vhost.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > > index 819296332913..42a8c2a13ab1 100644 > > --- a/drivers/vhost/vhost.h > > +++ b/drivers/vhost/vhost.h > > @@ -96,7 +96,7 @@ struct vhost_uaddr { > > }; > > #if defined(CONFIG_MMU_NOTIFIER) && ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE == 0 > > -#define VHOST_ARCH_CAN_ACCEL_UACCESS 1 > > +#define VHOST_ARCH_CAN_ACCEL_UACCESS 0 > > #else > > #define VHOST_ARCH_CAN_ACCEL_UACCESS 0 > > #endif