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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 E575BC10F0E for ; Thu, 18 Apr 2019 16:48:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B19FF21479 for ; Thu, 18 Apr 2019 16:48:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389649AbfDRQsF (ORCPT ); Thu, 18 Apr 2019 12:48:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49620 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388097AbfDRQsF (ORCPT ); Thu, 18 Apr 2019 12:48:05 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8C095319939D; Thu, 18 Apr 2019 16:48:04 +0000 (UTC) Received: from [10.36.112.46] (ovpn-112-46.ams2.redhat.com [10.36.112.46]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8194C60BEC; Thu, 18 Apr 2019 16:48:00 +0000 (UTC) Subject: Re: [PATCH] x86: kvm: hyper-v: deal with buggy TLB flush requests from WS2012 To: Sean Christopherson , Vitaly Kuznetsov Cc: kvm@vger.kernel.org, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Roman Kagan , linux-kernel@vger.kernel.org References: <20190320174320.9459-1-vkuznets@redhat.com> <20190418141752.GB17218@linux.intel.com> From: Paolo Bonzini Openpgp: preference=signencrypt Autocrypt: addr=pbonzini@redhat.com; prefer-encrypt=mutual; keydata= mQHhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAbQj UGFvbG8gQm9uemluaSA8cGJvbnppbmlAcmVkaGF0LmNvbT6JAg0EEwECACMFAlRCcBICGwMH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRB+FRAMzTZpsbceDp9IIN6BIA0Ol7MoB15E 11kRz/ewzryFY54tQlMnd4xxfH8MTQ/mm9I482YoSwPMdcWFAKnUX6Yo30tbLiNB8hzaHeRj jx12K+ptqYbg+cevgOtbLAlL9kNgLLcsGqC2829jBCUTVeMSZDrzS97ole/YEez2qFpPnTV0 VrRWClWVfYh+JfzpXmgyhbkuwUxNFk421s4Ajp3d8nPPFUGgBG5HOxzkAm7xb1cjAuJ+oi/K CHfkuN+fLZl/u3E/fw7vvOESApLU5o0icVXeakfSz0LsygEnekDbxPnE5af/9FEkXJD5EoYG SEahaEtgNrR4qsyxyAGYgZlS70vkSSYJ+iT2rrwEiDlo31MzRo6Ba2FfHBSJ7lcYdPT7bbk9 AO3hlNMhNdUhoQv7M5HsnqZ6unvSHOKmReNaS9egAGdRN0/GPDWr9wroyJ65ZNQsHl9nXBqE AukZNr5oJO5vxrYiAuuTSd6UI/xFkjtkzltG3mw5ao2bBpk/V/YuePrJsnPFHG7NhizrxttB nTuOSCMo45pfHQ+XYd5K1+Cv/NzZFNWscm5htJ0HznY+oOsZvHTyGz3v91pn51dkRYN0otqr bQ4tlFFuVjArBZcapSIe6NV8C4cEiSS5AQ0EVEJxcwEIAK+nUrsUz3aP2aBjIrX3a1+C+39R nctpNIPcJjFJ/8WafRiwcEuLjbvJ/4kyM6K7pWUIQftl1P8Woxwb5nqL7zEFHh5I+hKS3haO 5pgco//V0tWBGMKinjqntpd4U4Dl299dMBZ4rRbPvmI8rr63sCENxTnHhTECyHdGFpqSzWzy 97rH68uqMpxbUeggVwYkYihZNd8xt1+lf7GWYNEO/QV8ar/qbRPG6PEfiPPHQd/sldGYavmd //o6TQLSJsvJyJDt7KxulnNT8Q2X/OdEuVQsRT5glLaSAeVAABcLAEnNgmCIGkX7TnQF8a6w gHGrZIR9ZCoKvDxAr7RP6mPeS9sAEQEAAYkDEgQYAQIACQUCVEJxcwIbAgEpCRB+FRAMzTZp scBdIAQZAQIABgUCVEJxcwAKCRC/+9JfeMeug/SlCACl7QjRnwHo/VzENWD9G2VpUOd9eRnS DZGQmPo6Mp3Wy8vL7snGFBfRseT9BevXBSkxvtOnUUV2YbyLmolAODqUGzUI8ViF339poOYN i6Ffek0E19IMQ5+CilqJJ2d5ZvRfaq70LA/Ly9jmIwwX4auvXrWl99/2wCkqnWZI+PAepkcX JRD4KY2fsvRi64/aoQmcxTiyyR7q3/52Sqd4EdMfj0niYJV0Xb9nt8G57Dp9v3Ox5JeWZKXS krFqy1qyEIypIrqcMbtXM7LSmiQ8aJRM4ZHYbvgjChJKR4PsKNQZQlMWGUJO4nVFSkrixc9R Z49uIqQK3b3ENB1QkcdMg9cxsB0Onih8zR+Wp1uDZXnz1ekto+EivLQLqvTjCCwLxxJafwKI bqhQ+hGR9jF34EFur5eWt9jJGloEPVv0GgQflQaE+rRGe+3f5ZDgRe5Y/EJVNhBhKcafcbP8 MzmLRh3UDnYDwaeguYmxuSlMdjFL96YfhRBXs8tUw6SO9jtCgBvoOIBDCxxAJjShY4KIvEpK b2hSNr8KxzelKKlSXMtB1bbHbQxiQcerAipYiChUHq1raFc3V0eOyCXK205rLtknJHhM5pfG 6taABGAMvJgm/MrVILIxvBuERj1FRgcgoXtiBmLEJSb7akcrRlqe3MoPTntSTNvNzAJmfWhd SvP0G1WDLolqvX0OtKMppI91AWVu72f1kolJg43wbaKpRJg1GMkKEI3H+jrrlTBrNl/8e20m TElPRDKzPiowmXeZqFSS1A6Azv0TJoo9as+lWF+P4zCXt40+Zhh5hdHO38EV7vFAVG3iuay6 7ToF8Uy7tgc3mdH98WQSmHcn/H5PFYk3xTP3KHB7b0FZPdFPQXBZb9+tJeZBi9gMqcjMch+Y R8dmTcQRQX14bm5nXlBF7VpSOPZMR392LY7wzAvRdhz7aeIUkdO7VelaspFk2nT7wOj1Y6uL nRxQlLkBDQRUQnHuAQgAx4dxXO6/Zun0eVYOnr5GRl76+2UrAAemVv9Yfn2PbDIbxXqLff7o yVJIkw4WdhQIIvvtu5zH24iYjmdfbg8iWpP7NqxUQRUZJEWbx2CRwkMHtOmzQiQ2tSLjKh/c HeyFH68xjeLcinR7jXMrHQK+UCEw6jqi1oeZzGvfmxarUmS0uRuffAb589AJW50kkQK9VD/9 QC2FJISSUDnRC0PawGSZDXhmvITJMdD4TjYrePYhSY4uuIV02v028TVAaYbIhxvDY0hUQE4r 8ZbGRLn52bEzaIPgl1p/adKfeOUeMReg/CkyzQpmyB1TSk8lDMxQzCYHXAzwnGi8WU9iuE1P 0wARAQABiQHzBBgBAgAJBQJUQnHuAhsMAAoJEH4VEAzNNmmxp1EOoJy0uZggJm7gZKeJ7iUp eX4eqUtqelUw6gU2daz2hE/jsxsTbC/w5piHmk1H1VWDKEM4bQBTuiJ0bfo55SWsUNN+c9hh IX+Y8LEe22izK3w7mRpvGcg+/ZRG4DEMHLP6JVsv5GMpoYwYOmHnplOzCXHvmdlW0i6SrMsB Dl9rw4AtIa6bRwWLim1lQ6EM3PWifPrWSUPrPcw4OLSwFk0CPqC4HYv/7ZnASVkR5EERFF3+ 6iaaVi5OgBd81F1TCvCX2BEyIDRZLJNvX3TOd5FEN+lIrl26xecz876SvcOb5SL5SKg9/rCB ufdPSjojkGFWGziHiFaYhbuI2E+NfWLJtd+ZvWAAV+O0d8vFFSvriy9enJ8kxJwhC0ECbSKF Y+W1eTIhMD3aeAKY90drozWEyHhENf4l/V+Ja5vOnW+gCDQkGt2Y1lJAPPSIqZKvHzGShdh8 DduC0U3xYkfbGAUvbxeepjgzp0uEnBXfPTy09JGpgWbg0w91GyfT/ujKaGd4vxG2Ei+MMNDm S1SMx7wu0evvQ5kT9NPzyq8R2GIhVSiAd2jioGuTjX6AZCFv3ToO53DliFMkVTecLptsXaes uUHgL9dKIfvpm+rNXRn9wAwGjk0X/A== Message-ID: Date: Thu, 18 Apr 2019 18:47:56 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190418141752.GB17218@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Thu, 18 Apr 2019 16:48:04 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18/04/19 16:17, Sean Christopherson wrote: > On Wed, Mar 20, 2019 at 06:43:20PM +0100, Vitaly Kuznetsov wrote: >> 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. >> >> Signed-off-by: Vitaly Kuznetsov >> --- >> arch/x86/kvm/hyperv.c | 12 +++++++++++- >> 1 file changed, 11 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c >> index 421899f6ad7b..5887f7d22ac6 100644 >> --- a/arch/x86/kvm/hyperv.c >> +++ b/arch/x86/kvm/hyperv.c >> @@ -1371,7 +1371,17 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *current_vcpu, u64 ingpa, >> >> valid_bank_mask = BIT_ULL(0); >> sparse_banks[0] = flush.processor_mask; >> - all_cpus = flush.flags & HV_FLUSH_ALL_PROCESSORS; >> + >> + /* >> + * WS2012 seems to be buggy, under certain conditions it is >> + * possible to observe requests with processor_mask = 0x0 and >> + * no HV_FLUSH_ALL_PROCESSORS flag set. It also seems that > > "and no HV_FLUSH_ALL_PROCESSORS flag set" is awkward, and probably > extraneous. The whole comment is a probably a bit more verbose than it > needs to be, e.g. most readers won't care how we came to the conclusion > that 'processor_mask == 0', and those that care about the background will > read the changelog anyways. > > Maybe something like this: > > /* > * Some Windows versions, e.g. WS2012, use processor_mask = 0 > * in lieu of the dedicated flag to flush all processors. > */ Hmm, not really. "In lieu" seems intentional. "without" is more accurate. My take: * Work around possible WS2012 bug: it sends hypercalls * with processor_mask = 0x0 and HV_FLUSH_ALL_PROCESSORS clear, * while also expecting us to flush something and crashing if * we don't. Let's treat processor_mask == 0 same as * HV_FLUSH_ALL_PROCESSORS. */ Paolo > > >> + * Windows actually expects us to flush something and crashes >> + * otherwise. Let's treat processor_mask == 0 same as >> + * HV_FLUSH_ALL_PROCESSORS. >> + */ >> + all_cpus = (flush.flags & HV_FLUSH_ALL_PROCESSORS) || >> + (flush.processor_mask == 0); > > Nits: > > Personal preference, but I like '!flush.processor_mask' in this case as it > immediately conveys that we're handling the scenario where the guest didn't > set a mask. Then there wouldn't be a visual need for the second set of > parentheses. > > Aligning its indentation with the first first chunk of the statement would > also be nice, but again, personal preference. :-) > >> } else { >> if (unlikely(kvm_read_guest(kvm, ingpa, &flush_ex, >> sizeof(flush_ex)))) >> -- >> 2.20.1 >>