Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752744AbbKPVA6 (ORCPT ); Mon, 16 Nov 2015 16:00:58 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:40737 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751903AbbKPVAz (ORCPT ); Mon, 16 Nov 2015 16:00:55 -0500 Subject: Re: [PATCH v2] x86/irq: Probe for PIC presence before allocating descs for legacy IRQs To: Vitaly Kuznetsov , x86@kernel.org References: <1446543614-3621-1-git-send-email-vkuznets@redhat.com> Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Jiang Liu , "K. Y. Srinivasan" , linux-kernel@vger.kernel.org, xen-devel From: Boris Ostrovsky Message-ID: <564A43F5.30602@oracle.com> Date: Mon, 16 Nov 2015 16:00:37 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <1446543614-3621-1-git-send-email-vkuznets@redhat.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5572 Lines: 98 On 11/03/2015 04:40 AM, Vitaly Kuznetsov wrote: > Commit d32932d02e18 ("x86/irq: Convert IOAPIC to use hierarchical irqdomain > interfaces") brought a regression for Hyper-V Gen2 instances. These > instances don't have i8259 legacy PIC but they use legacy IRQs for serial > port, rtc, and acpi. With this commit included we end up with these IRQs > not initialized. Earlier, there was a special workaround for legacy IRQs > in mp_map_pin_to_irq() doing mp_irqdomain_map() without looking at > nr_legacy_irqs() and now we fail in __irq_domain_alloc_irqs() when > irq_domain_alloc_descs() returns -EEXIST. > > The essence of the issue seems to be that early_irq_init() calls > arch_probe_nr_irqs() to figure out the number of legacy IRQs before > we probe for i8259 and gets 16. Later when init_8259A() is called we switch > to NULL legacy PIC and nr_legacy_irqs() starts to return 0 but we already > have 16 descs allocated. > > Solve the issue by separating i8259 probe from init and calling it in > arch_probe_nr_irqs() before we actually use nr_legacy_irqs() information. > > Fixes: d32932d02e18 ("x86/irq: Convert IOAPIC to use hierarchical irqdomain interfaces") > Signed-off-by: Vitaly Kuznetsov This breaks PV Xen with [ 0.000000] NR_IRQS:33024 nr_irqs:440 0 ... [ 6.949434] BUG: unable to handle kernel NULL pointer dereference at (null) [ 6.957564] IP: [] xen_irq_init+0x29/0xe0 [ 6.963385] PGD 0 [ 6.965528] Oops: 0002 [#1] SMP [ 6.968927] Modules linked in: [ 6.972152] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.3.0upstream-12231-g3e546cd-dirty #1 [ 6.980842] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./To be filled by O.E.M., BIOS 080014 07/18/2008 [ 6.992123] task: ffff880037992d00 ti: ffff880037994000 task.ti: ffff880037994000 [ 6.999904] RIP: e030:[] [] xen_irq_init+0x29/0xe0 [ 7.008231] RSP: e02b:ffff880037997c48 EFLAGS: 00010246 [ 7.013778] RAX: 0000000000000001 RBX: 0000000000000009 RCX: 0000000000000058 [ 7.021204] RDX: 0000000000000000 RSI: 00000000024080c0 RDI: ffff880038000d88 [ 7.028634] RBP: ffff880037997c58 R08: 0000000000000000 R09: ffff880037997be8 [ 7.036062] R10: 0000000000000000 R11: ffff880038000df8 R12: 0000000000000009 [ 7.043491] R13: 0000000000000001 R14: 0000000000000009 R15: ffffffff819dfa04 [ 7.050922] FS: 0000000000000000(0000) GS:ffff88003de00000(0000) knlGS:0000000000000000 [ 7.059343] CS: e033 DS: 0000 ES: 0000 CR0: 000000008005003b [ 7.065330] CR2: 0000000000000000 CR3: 0000000001c0b000 CR4: 0000000000000660 [ 7.072759] Stack: [ 7.074905] 0000000000000009 0000000000000009 ffff880037997cb8 ffffffff8143e5f1 [ 7.082601] 00ff880037997c88 0000000000000000 ffffffff81832820 0000000000000009 [ 7.090299] ffff880037997da4 0000000000000009 0000000000000000 00000000ffffffff [ 7.097999] Call Trace: [ 7.100601] [] xen_bind_pirq_gsi_to_irq+0x81/0x210 [ 7.107313] [] xen_register_pirq.clone.0+0x9c/0xf0 [ 7.114026] [] acpi_register_gsi_xen+0x61/0xd0 [ 7.120378] [] acpi_gsi_to_irq+0x69/0x80 [ 7.126199] [] ? acpi_ev_remove_all_sci_handlers+0xa5/0xa5 [ 7.133626] [] acpi_os_install_interrupt_handler+0x47/0xc5 [ 7.141053] [] ? acpi_ev_gpe_initialize+0x230/0x240 [ 7.147861] [] acpi_ev_install_sci_handler+0x3f/0x6a [ 7.154752] [] ? acpi_ev_initialize_events+0x138/0x151 [ 7.161823] [] acpi_ev_install_xrupt_handlers+0x54/0x10b [ 7.169074] [] acpi_enable_subsystem+0x22d/0x27f [ 7.175605] [] ? acpi_early_init+0xeb/0xeb [ 7.181599] [] acpi_init+0x75/0x294 [ 7.186974] [] ? video_setup+0x85/0x85 [ 7.192612] [] ? acpi_early_init+0xeb/0xeb [ 7.198607] [] do_one_initcall+0x81/0x1b0 [ 7.204516] [] kernel_init_freeable+0x171/0x20c [ 7.210958] [] ? kernel_init_freeable+0x20c/0x20c [ 7.217583] [] ? rest_init+0x90/0x90 [ 7.223046] [] kernel_init+0x9/0xe0 [ 7.228416] [] ret_from_fork+0x3f/0x70 [ 7.234054] [] ? rest_init+0x90/0x90 [ 7.239513] Code: 00 00 55 48 89 e5 41 54 53 89 fb e8 e2 65 cc ff 31 d2 48 85 c0 74 08 48 8b 50 10 48 83 c2 18 48 8b 05 ec 72 3d 00 be c0 80 40 02 <48> 89 02 48 8b 05 e5 72 3d 00 48 89 42 08 48 8b 05 e2 72 3d 00 [ 7.259023] RIP [] xen_irq_init+0x29/0xe0 [ 7.264932] RSP [ 7.268598] CR2: 0000000000000000 [ 7.272095] ---[ end trace 725f5e1483cadab0 ]--- [ 7.276921] Kernel panic - not syncing: Fatal exception (XEN) Domain 0 crashed: rebooting machine in 5 seconds. Xen expects legacy interrupts to be there (pretty much for the same reason as Hyper-V does) and with this change arch_probe_nr_irqs() returns zero and no descriptors are allocated. We can allocate those descriptors as needed in xen_irq_init() (if we know that IRQs are legacy), although that would look somewhat ugly and out of place. -boris -boris -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/