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 BB1B5C433E2 for ; Fri, 11 Sep 2020 07:46:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7E1E221D92 for ; Fri, 11 Sep 2020 07:46:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725784AbgIKHpy (ORCPT ); Fri, 11 Sep 2020 03:45:54 -0400 Received: from smtpout1.mo804.mail-out.ovh.net ([79.137.123.220]:36643 "EHLO smtpout1.mo804.mail-out.ovh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725800AbgIKHpt (ORCPT ); Fri, 11 Sep 2020 03:45:49 -0400 Received: from mxplan5.mail.ovh.net (unknown [10.109.156.13]) by mo804.mail-out.ovh.net (Postfix) with ESMTPS id 6BEC660619AB; Fri, 11 Sep 2020 09:45:43 +0200 (CEST) Received: from kaod.org (37.59.142.96) 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 09:45:42 +0200 Authentication-Results: garm.ovh; auth=pass (GARM-96R001d0b0f908-b7f8-4ded-830f-0b985388e565, 864FBEA0465FE1F0C66A9C6AC37977A76827B8ED) smtp.auth=groug@kaod.org Date: Fri, 11 Sep 2020 09:45:36 +0200 From: Greg Kurz To: Fabiano Rosas CC: , , , , , Subject: Re: [PATCH] KVM: PPC: Book3S HV: Do not allocate HPT for a nested guest Message-ID: <20200911094536.72dd700a@bahia.lan> In-Reply-To: <20200911041607.198092-1-farosas@linux.ibm.com> References: <20200911041607.198092-1-farosas@linux.ibm.com> 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="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [37.59.142.96] X-ClientProxiedBy: DAG9EX1.mxp5.local (172.16.2.81) To DAG8EX1.mxp5.local (172.16.2.71) X-Ovh-Tracer-GUID: dfe5079d-0ecb-41fa-bf33-af55cbc276d2 X-Ovh-Tracer-Id: 3109454068212603241 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: -100 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgeduiedrudehkedguddvhecutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfqggfjpdevjffgvefmvefgnecuuegrihhlohhuthemucehtddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpeffhffvuffkjghfofggtgfgihesthejredtredtvdenucfhrhhomhepifhrvghgucfmuhhriicuoehgrhhouhhgsehkrghougdrohhrgheqnecuggftrfgrthhtvghrnhepfedutdeijeejveehkeeileetgfelteekteehtedtieefffevhffflefftdefleejnecukfhppedtrddtrddtrddtpdefjedrheelrddugedvrdelieenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepmhhouggvpehsmhhtphdqohhuthdphhgvlhhopehmgihplhgrnhehrdhmrghilhdrohhvhhdrnhgvthdpihhnvghtpedtrddtrddtrddtpdhmrghilhhfrhhomhepghhrohhugheskhgrohgurdhorhhgpdhrtghpthhtohepuggrvhhiugesghhisghsohhnrdgurhhophgsvggrrhdrihgurdgruh Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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; > + break; > + } > + > r = -EFAULT; > if (get_user(htab_order, (u32 __user *)argp)) > break;