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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 16ADEC43461 for ; Fri, 11 Sep 2020 08:17:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AFD9D21D40 for ; Fri, 11 Sep 2020 08:17:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725824AbgIKIRU convert rfc822-to-8bit (ORCPT ); Fri, 11 Sep 2020 04:17:20 -0400 Received: from smtpout1.mo529.mail-out.ovh.net ([178.32.125.2]:36175 "EHLO smtpout1.mo529.mail-out.ovh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725550AbgIKIRR (ORCPT ); Fri, 11 Sep 2020 04:17:17 -0400 Received: from mxplan5.mail.ovh.net (unknown [10.109.156.13]) by mo529.mail-out.ovh.net (Postfix) with ESMTPS id BD11759E825E; Fri, 11 Sep 2020 10:17:14 +0200 (CEST) Received: from kaod.org (37.59.142.100) by DAG8EX1.mxp5.local (172.16.2.71) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2044.4; Fri, 11 Sep 2020 10:17:14 +0200 Authentication-Results: garm.ovh; auth=pass (GARM-100R003ee35ee02-b75a-4f31-b232-c412f1676161, 864FBEA0465FE1F0C66A9C6AC37977A76827B8ED) smtp.auth=groug@kaod.org Date: Fri, 11 Sep 2020 10:17:13 +0200 From: Greg Kurz To: Michal =?UTF-8?B?U3VjaMOhbmVr?= CC: Fabiano Rosas , , , , Subject: Re: [PATCH] KVM: PPC: Book3S HV: Do not allocate HPT for a nested guest Message-ID: <20200911101713.38e3c442@bahia.lan> In-Reply-To: <20200911080810.GD29521@kitsune.suse.cz> References: <20200911041607.198092-1-farosas@linux.ibm.com> <20200911094536.72dd700a@bahia.lan> <20200911100133.49d22e82@bahia.lan> <20200911080810.GD29521@kitsune.suse.cz> X-Mailer: Claws Mail 3.17.6 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Originating-IP: [37.59.142.100] X-ClientProxiedBy: DAG9EX2.mxp5.local (172.16.2.82) To DAG8EX1.mxp5.local (172.16.2.71) X-Ovh-Tracer-GUID: 1a7fb1dc-c974-4939-82b2-b46fcc54d8bb X-Ovh-Tracer-Id: 3641723252167055654 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: -100 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgeduiedrudehledgtdefucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecuqfggjfdpvefjgfevmfevgfenuceurghilhhouhhtmecuhedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmnecujfgurhepfffhvffukfgjfhfogggtgfhisehtqhertdertdejnecuhfhrohhmpefirhgvghcumfhurhiiuceoghhrohhugheskhgrohgurdhorhhgqeenucggtffrrghtthgvrhhnpedvgfdvieeukedvfeefleefkeevgfefgfejieeiveegjeduveeifefhleeghfefgeenucffohhmrghinhepohhpvghnghhrohhuphdrohhrghenucfkpheptddrtddrtddrtddpfeejrdehledrudegvddruddttdenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhhouggvpehsmhhtphdqohhuthdphhgvlhhopehmgihplhgrnhehrdhmrghilhdrohhvhhdrnhgvthdpihhnvghtpedtrddtrddtrddtpdhmrghilhhfrhhomhepghhrohhugheskhgrohgurdhorhhgpdhrtghpthhtohepuggrvhhiugesghhisghsohhnrdgurhhophgsvggrrhdrihgurdgruh Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, 11 Sep 2020 10:08:10 +0200 Michal Suchánek wrote: > On Fri, Sep 11, 2020 at 10:01:33AM +0200, Greg Kurz wrote: > > On Fri, 11 Sep 2020 09:45:36 +0200 > > Greg Kurz wrote: > > > > > On Fri, 11 Sep 2020 01:16:07 -0300 > > > Fabiano Rosas wrote: > > > > > > > The current nested KVM code does not support HPT guests. This is > > > > informed/enforced in some ways: > > > > > > > > - Hosts < P9 will not be able to enable the nested HV feature; > > > > > > > > - The nested hypervisor MMU capabilities will not contain > > > > KVM_CAP_PPC_MMU_HASH_V3; > > > > > > > > - QEMU reflects the MMU capabilities in the > > > > 'ibm,arch-vec-5-platform-support' device-tree property; > > > > > > > > - The nested guest, at 'prom_parse_mmu_model' ignores the > > > > 'disable_radix' kernel command line option if HPT is not supported; > > > > > > > > - The KVM_PPC_CONFIGURE_V3_MMU ioctl will fail if trying to use HPT. > > > > > > > > There is, however, still a way to start a HPT guest by using > > > > max-compat-cpu=power8 at the QEMU machine options. This leads to the > > > > guest being set to use hash after QEMU calls the KVM_PPC_ALLOCATE_HTAB > > > > ioctl. > > > > > > > > With the guest set to hash, the nested hypervisor goes through the > > > > entry path that has no knowledge of nesting (kvmppc_run_vcpu) and > > > > crashes when it tries to execute an hypervisor-privileged (mtspr > > > > HDEC) instruction at __kvmppc_vcore_entry: > > > > > > > > root@L1:~ $ qemu-system-ppc64 -machine pseries,max-cpu-compat=power8 ... > > > > > > > > > > > > [ 538.543303] CPU: 83 PID: 25185 Comm: CPU 0/KVM Not tainted 5.9.0-rc4 #1 > > > > [ 538.543355] NIP: c00800000753f388 LR: c00800000753f368 CTR: c0000000001e5ec0 > > > > [ 538.543417] REGS: c0000013e91e33b0 TRAP: 0700 Not tainted (5.9.0-rc4) > > > > [ 538.543470] MSR: 8000000002843033 CR: 22422882 XER: 20040000 > > > > [ 538.543546] CFAR: c00800000753f4b0 IRQMASK: 3 > > > > GPR00: c0080000075397a0 c0000013e91e3640 c00800000755e600 0000000080000000 > > > > GPR04: 0000000000000000 c0000013eab19800 c000001394de0000 00000043a054db72 > > > > GPR08: 00000000003b1652 0000000000000000 0000000000000000 c0080000075502e0 > > > > GPR12: c0000000001e5ec0 c0000007ffa74200 c0000013eab19800 0000000000000008 > > > > GPR16: 0000000000000000 c00000139676c6c0 c000000001d23948 c0000013e91e38b8 > > > > GPR20: 0000000000000053 0000000000000000 0000000000000001 0000000000000000 > > > > GPR24: 0000000000000001 0000000000000001 0000000000000000 0000000000000001 > > > > GPR28: 0000000000000001 0000000000000053 c0000013eab19800 0000000000000001 > > > > [ 538.544067] NIP [c00800000753f388] __kvmppc_vcore_entry+0x90/0x104 [kvm_hv] > > > > [ 538.544121] LR [c00800000753f368] __kvmppc_vcore_entry+0x70/0x104 [kvm_hv] > > > > [ 538.544173] Call Trace: > > > > [ 538.544196] [c0000013e91e3640] [c0000013e91e3680] 0xc0000013e91e3680 (unreliable) > > > > [ 538.544260] [c0000013e91e3820] [c0080000075397a0] kvmppc_run_core+0xbc8/0x19d0 [kvm_hv] > > > > [ 538.544325] [c0000013e91e39e0] [c00800000753d99c] kvmppc_vcpu_run_hv+0x404/0xc00 [kvm_hv] > > > > [ 538.544394] [c0000013e91e3ad0] [c0080000072da4fc] kvmppc_vcpu_run+0x34/0x48 [kvm] > > > > [ 538.544472] [c0000013e91e3af0] [c0080000072d61b8] kvm_arch_vcpu_ioctl_run+0x310/0x420 [kvm] > > > > [ 538.544539] [c0000013e91e3b80] [c0080000072c7450] kvm_vcpu_ioctl+0x298/0x778 [kvm] > > > > [ 538.544605] [c0000013e91e3ce0] [c0000000004b8c2c] sys_ioctl+0x1dc/0xc90 > > > > [ 538.544662] [c0000013e91e3dc0] [c00000000002f9a4] system_call_exception+0xe4/0x1c0 > > > > [ 538.544726] [c0000013e91e3e20] [c00000000000d140] system_call_common+0xf0/0x27c > > > > [ 538.544787] Instruction dump: > > > > [ 538.544821] f86d1098 60000000 60000000 48000099 e8ad0fe8 e8c500a0 e9264140 75290002 > > > > [ 538.544886] 7d1602a6 7cec42a6 40820008 7d0807b4 <7d164ba6> 7d083a14 f90d10a0 480104fd > > > > [ 538.544953] ---[ end trace 74423e2b948c2e0c ]--- > > > > > > > > This patch makes the KVM_PPC_ALLOCATE_HTAB ioctl fail when running in > > > > the nested hypervisor, causing QEMU to abort. > > > > > > > > Reported-by: Satheesh Rajendran > > > > Signed-off-by: Fabiano Rosas > > > > --- > > > > > > LGTM > > > > > > Reviewed-by: Greg Kurz > > > > > > > arch/powerpc/kvm/book3s_hv.c | 6 ++++++ > > > > 1 file changed, 6 insertions(+) > > > > > > > > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c > > > > index 4ba06a2a306c..764b6239ef72 100644 > > > > --- a/arch/powerpc/kvm/book3s_hv.c > > > > +++ b/arch/powerpc/kvm/book3s_hv.c > > > > @@ -5250,6 +5250,12 @@ static long kvm_arch_vm_ioctl_hv(struct file *filp, > > > > case KVM_PPC_ALLOCATE_HTAB: { > > > > u32 htab_order; > > > > > > > > + /* If we're a nested hypervisor, we currently only support radix */ > > > > + if (kvmhv_on_pseries()) { > > > > + r = -EOPNOTSUPP; > > > > According to POSIX [1]: > > > > [ENOTSUP] > > Not supported. The implementation does not support the requested feature or value. > > > > [EOPNOTSUPP] > > Operation not supported on socket. The type of socket (address family or protocol) does not support the requested operation. A conforming implementation may assign the same values for [EOPNOTSUPP] and [ENOTSUP]. > > > > Even if these two happen to be equal in linux, it seems that ENOTSUP, which > > doesn't refer to sockets, is more appropriate. > > > > [1] https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html > > Which in Linux kernel maps to a completely bogus value not recognized by > userspace. > There's no such thing as ENOTSUP in Linux actually :) Linux has ENOTSUPP which indeed doesn't map to anything usable by userspace... very unfortunate naming :-( > So when you mean ENOTSUP use EOPNOTSUPP in Linux. > Right. So this patch is good as it is. Cheers, -- Greg > Thanks > > Michal