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Tue, 7 Apr 2020 07:49:10 +0000 (UTC) Received: from [10.36.114.167] (ovpn-114-167.ams2.redhat.com [10.36.114.167]) by smtp.corp.redhat.com (Postfix) with ESMTP id A4DB960BE1; Tue, 7 Apr 2020 07:49:08 +0000 (UTC) Subject: Re: [PATCH v2 1/5] KVM: s390: vsie: Fix region 1 ASCE sanity shadow address checks To: Christian Borntraeger , kvm@vger.kernel.org Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Vasily Gorbik , Heiko Carstens , Cornelia Huck , Janosch Frank , stable@vger.kernel.org References: <20200403153050.20569-1-david@redhat.com> <20200403153050.20569-2-david@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: Date: Tue, 7 Apr 2020 09:49:07 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07.04.20 09:33, Christian Borntraeger wrote: > > On 03.04.20 17:30, David Hildenbrand wrote: >> In case we have a region 1 ASCE, our shadow/g3 address can have any value. >> Unfortunately, (-1UL << 64) is undefined and triggers sometimes, >> rejecting valid shadow addresses when trying to walk our shadow table >> hierarchy. >> >> The result is that the prefix cannot get mapped and will loop basically >> forever trying to map it (-EAGAIN loop). >> >> After all, the broken check is only a sanity check, our table shadowing >> code in kvm_s390_shadow_tables() already checks these conditions, injecting >> proper translation exceptions. Turn it into a WARN_ON_ONCE(). > > After some testing I now triggered this warning: > > [ 541.633114] ------------[ cut here ]------------ > [ 541.633128] WARNING: CPU: 38 PID: 2812 at arch/s390/mm/gmap.c:799 gmap_shadow_pgt_lookup+0x98/0x1a0 > [ 541.633129] Modules linked in: vhost_net vhost macvtap macvlan tap kvm xt_CHECKSUM xt_MASQUERADE nf_nat_tftp nf_conntrack_tftp xt_CT tun bridge stp llc xt_tcpudp ip6t_REJECT nf_reject_ipv6 ip6t_rpfilter ipt_REJECT nf_reject_ipv4 xt_conntrack ip6table_nat ip6table_mangle ip6table_raw ip6table_security iptable_nat nf_nat iptable_mangle iptable_raw iptable_security nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nfnetlink ip6table_filter ip6_tables iptable_filter rpcrdma sunrpc rdma_ucm rdma_cm iw_cm ib_cm configfs mlx5_ib s390_trng ghash_s390 prng aes_s390 ib_uverbs des_s390 ib_core libdes sha3_512_s390 genwqe_card sha3_256_s390 vfio_ccw crc_itu_t vfio_mdev sha512_s390 mdev vfio_iommu_type1 sha1_s390 vfio eadm_sch zcrypt_cex4 sch_fq_codel ip_tables x_tables mlx5_core sha256_s390 sha_common pkey zcrypt rng_core autofs4 > [ 541.633164] CPU: 38 PID: 2812 Comm: CPU 0/KVM Not tainted 5.6.0+ #354 > [ 541.633166] Hardware name: IBM 3906 M04 704 (LPAR) > [ 541.633167] Krnl PSW : 0704d00180000000 00000014e05dc454 (gmap_shadow_pgt_lookup+0x9c/0x1a0) > [ 541.633169] R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:1 PM:0 RI:0 EA:3 > [ 541.633171] Krnl GPRS: 0000000000000000 0000001f00000000 0000001f487b8000 ffffffff80000000 > [ 541.633172] ffffffffffffffff 000003e003defa18 000003e003defa1c 000003e003defa18 > [ 541.633173] fffffffffffff000 000003e003defa18 000003e003defa28 0000001f70e06300 > [ 541.633174] 0000001f43484000 00000000043ed200 000003e003def978 000003e003def920 > [ 541.633203] Krnl Code: 00000014e05dc448: b9800038 ngr %r3,%r8 > 00000014e05dc44c: a7840014 brc 8,00000014e05dc474 > #00000014e05dc450: af000000 mc 0,0 > >00000014e05dc454: a728fff5 lhi %r2,-11 > 00000014e05dc458: a7180000 lhi %r1,0 > 00000014e05dc45c: b2fa0070 niai 7,0 > 00000014e05dc460: 4010b04a sth %r1,74(%r11) > 00000014e05dc464: b9140022 lgfr %r2,%r2 > [ 541.633215] Call Trace: > [ 541.633218] [<00000014e05dc454>] gmap_shadow_pgt_lookup+0x9c/0x1a0 > [ 541.633257] [<000003ff804c57d6>] kvm_s390_shadow_fault+0x66/0x1e8 [kvm] > [ 541.633265] [<000003ff804c72dc>] vsie_run+0x43c/0x710 [kvm] > [ 541.633273] [<000003ff804c85ca>] kvm_s390_handle_vsie+0x632/0x750 [kvm] > [ 541.633281] [<000003ff804c123c>] kvm_s390_handle_b2+0x84/0x4e0 [kvm] > [ 541.633289] [<000003ff804b46b2>] kvm_handle_sie_intercept+0x172/0xcb8 [kvm] > [ 541.633297] [<000003ff804b18a8>] __vcpu_run+0x658/0xc90 [kvm] > [ 541.633305] [<000003ff804b2920>] kvm_arch_vcpu_ioctl_run+0x248/0x858 [kvm] > [ 541.633313] [<000003ff8049d454>] kvm_vcpu_ioctl+0x284/0x7b0 [kvm] > [ 541.633316] [<00000014e087d5ae>] ksys_ioctl+0xae/0xe8 > [ 541.633318] [<00000014e087d652>] __s390x_sys_ioctl+0x2a/0x38 > [ 541.633323] [<00000014e0ff02a2>] system_call+0x2a6/0x2c8 > [ 541.633323] Last Breaking-Event-Address: > [ 541.633334] [<000003ff804983e0>] kvm_running_vcpu+0x3ea9ee997d8/0x3ea9ee99950 [kvm] > [ 541.633335] ---[ end trace f69b6021855ea189 ]--- > > > Unfortunately no dump at that point in time. > I have other tests which are clearly fixed by this patch, so we should propbably go forward anyway. > Question is, is this just another bug we need to fix or is the assumption that somebody else checked > all conditions so we can warn false? Yeah, I think it is via kvm_s390_shadow_fault()->gmap_shadow_pgt_lookup()->gmap_table_walk() where we just peek if there is already something shadowed. If not, we go via the full kvm_s390_shadow_tables() path. So we could either do sanity checks in gmap_shadow_pgt_lookup(), or rather drop the WARN_ON_ONCE. I think the latter makes sense, now that we understood the problem. -- Thanks, David / dhildenb