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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 588DDC10F0B for ; Thu, 18 Apr 2019 07:14:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 297472186A for ; Thu, 18 Apr 2019 07:14:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388082AbfDRHOG (ORCPT ); Thu, 18 Apr 2019 03:14:06 -0400 Received: from mail-wr1-f51.google.com ([209.85.221.51]:35538 "EHLO mail-wr1-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726873AbfDRHOG (ORCPT ); Thu, 18 Apr 2019 03:14:06 -0400 Received: by mail-wr1-f51.google.com with SMTP id o12so1602685wrn.2 for ; Thu, 18 Apr 2019 00:14:05 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=KDmQA5vkLWxGPxFVassSlW3/WlZCgZYWuWBWwkSTvgM=; b=iv2tEtSXum6udthqboNsaXojDrCO50sc6WHJUnRtCu0R8PIWeEE6UaQDdF5zS6VXf5 rU9RKnCEiTsfjvj+gf6N8VsFMIRnsRHIvb4TQ0Oq7OmGCw3HOTkEvQjv9EFRd+3hK8fQ h10PvYfZnONg1enUFKCXdSZzIZNXbqm+uEfjVqw8zUkZ3s0tFfR0SPBKZzWx59OyYRVX dpr9Ett6x/NGmLwjZ/SkNmX+WlK41LKE/jB1X7vPp8ew5ciUHYCtzqOnN0pG2nqvz1py 2PcZI0kMmLetCAtgrmezq+L1IB5sSfhHwuag1k81pLmwopJ8gwrldV2vdm12J3aYPpTS trbw== X-Gm-Message-State: APjAAAXvgRJOS4zeHU/NlrLHDlOLZ6rya+mim13rFjaM6Pxg3OiS5Svf uN1CtWf+YctN30+EuH1r48K8OG3Kx+k= X-Google-Smtp-Source: APXvYqxe1pcPMAR1fisjXVqfI4GbBB39W0W1lpy/X6JxSfJqQVcR3DlM8Eoc6xWJqgCMstR9hU9Ufg== X-Received: by 2002:adf:e703:: with SMTP id c3mr6467850wrm.98.1555571644645; Thu, 18 Apr 2019 00:14:04 -0700 (PDT) Received: from vitty.brq.redhat.com (ip-213-220-248-130.net.upcbroadband.cz. [213.220.248.130]) by smtp.gmail.com with ESMTPSA id j7sm1267661wrt.96.2019.04.18.00.14.03 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 18 Apr 2019 00:14:03 -0700 (PDT) From: Vitaly Kuznetsov To: kvm@vger.kernel.org Cc: Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , Roman Kagan , linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86: kvm: hyper-v: deal with buggy TLB flush requests from WS2012 In-Reply-To: <20190320174320.9459-1-vkuznets@redhat.com> References: <20190320174320.9459-1-vkuznets@redhat.com> Date: Thu, 18 Apr 2019 09:14:03 +0200 Message-ID: <87sguf23b8.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Vitaly Kuznetsov writes: > It was reported that with some special Multi Processor Group configuration, > e.g: > bcdedit.exe /set groupsize 1 > bcdedit.exe /set maxgroup on > bcdedit.exe /set groupaware on > for a 16-vCPU guest WS2012 shows BSOD on boot when PV TLB flush mechanism > is in use. > > Tracing kvm_hv_flush_tlb immediately reveals the issue: > > kvm_hv_flush_tlb: processor_mask 0x0 address_space 0x0 flags 0x2 > > The only flag set in this request is HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES, > however, processor_mask is 0x0 and no HV_FLUSH_ALL_PROCESSORS is specified. > We don't flush anything and apparently it's not what Windows expects. > > TLFS doesn't say anything about such requests and newer Windows versions > seem to be unaffected. This all feels like a WS2012 bug, which is, however, > easy to workaround in KVM: let's flush everything when we see an empty > flush request, over-flushing doesn't hurt. > Ping) I understand the lack of interest towards this ugly hack but I don't see a better option ... -- Vitaly