* Masayoshi Mizuma <msys.miz...@gmail.com> wrote: > From: Masayoshi Mizuma <m.miz...@jp.fujitsu.com> > > When a physical cpu is hot-removed, the following warning message > are shown while the uncore device is removing in uncore_pci_remove(). > > WARNING: CPU: 120 PID: 5 at arch/x86/events/intel/uncore.c:988 > uncore_pci_remove+0xf1/0x110 > ... > CPU: 120 PID: 5 Comm: kworker/u1024:0 Not tainted 4.15.0-rc8 #1 > Workqueue: kacpi_hotplug acpi_hotplug_work_fn > ... > Call Trace: > pci_device_remove+0x36/0xb0 > device_release_driver_internal+0x145/0x210 > pci_stop_bus_device+0x76/0xa0 > pci_stop_root_bus+0x44/0x60 > acpi_pci_root_remove+0x1f/0x80 > acpi_bus_trim+0x54/0x90 > acpi_bus_trim+0x2e/0x90 > acpi_device_hotplug+0x2bc/0x4b0 > acpi_hotplug_work_fn+0x1a/0x30 > process_one_work+0x141/0x340 > worker_thread+0x47/0x3e0 > kthread+0xf5/0x130 > > When uncore_pci_remove() runs, it tries to get package id to > clear the value of uncore_extra_pci_dev[].dev[] by using > topology_phys_to_logical_pkg(). The warning messesage are > shown because topology_phys_to_logical_pkg() returns -1. > > arch/x86/events/intel/uncore.c: > static void uncore_pci_remove(struct pci_dev *pdev) > { > ... > phys_id = uncore_pcibus_to_physid(pdev->bus); > ... > pkg = topology_phys_to_logical_pkg(phys_id); //returns -1 > for (i = 0; i < UNCORE_EXTRA_PCI_DEV_MAX; i++) { > if (uncore_extra_pci_dev[pkg].dev[i] == pdev) { > uncore_extra_pci_dev[pkg].dev[i] = NULL; > break; > } > } > WARN_ON_ONCE(i >= UNCORE_EXTRA_PCI_DEV_MAX); //HERE!! > > topology_phys_to_logical_pkg() tries to find > cpuinfo_x86->phys_proc_id that matches the phys_pkg argument. > > arch/x86/kernel/smpboot.c: > int topology_phys_to_logical_pkg(unsigned int phys_pkg) > { > int cpu; > > for_each_possible_cpu(cpu) { > struct cpuinfo_x86 *c = &cpu_data(cpu); > > if (c->initialized && c->phys_proc_id == phys_pkg) > return c->logical_proc_id; > } > return -1; > } > > However, the phys_proc_id is already set to 0 by remove_siblinginfo() > when the cpu was offlined. > So, topology_phys_to_logical_pkg() cannot find correct the > logical_proc_id and always returns -1. > As the result, uncore_pci_remove() calls WARN_ON_ONCE() and the warning > messages are shown. > > To avoid this, remove the setting from remove_siblinginfo(). > There is no influence about the removing because phys_proc_id is not > used after it is hot-removed and it is re-set while hot-adding.
So I think this fix goes beyond fixing a 'warning', if we get -1 for 'pkg': > pkg = topology_phys_to_logical_pkg(phys_id); //returns -1 > for (i = 0; i < UNCORE_EXTRA_PCI_DEV_MAX; i++) { > if (uncore_extra_pci_dev[pkg].dev[i] == pdev) { > uncore_extra_pci_dev[pkg].dev[i] = NULL; ... then that creates two _real_ bugs AFAICS: 1) we dereference uncore_extra_pci_dev[] with a negative index 2) we fail to clean up a stale pointer in uncore_extra_pci_dev[][] So I've rewritten your changelog accordingly - see the attached patch. I have also added a Cc: stable tag. Thanks, Ingo ===================> >From 295cc7eb314eb3321fb6d67ca6f7305f5c50d10f Mon Sep 17 00:00:00 2001 From: Masayoshi Mizuma <m.miz...@jp.fujitsu.com> Date: Thu, 8 Feb 2018 09:19:08 -0500 Subject: [PATCH] x86/smpboot: Fix uncore_pci_remove() indexing bug when hot-removing a physical CPU When a physical CPU is hot-removed, the following warning messages are shown while the uncore device is removed in uncore_pci_remove(): WARNING: CPU: 120 PID: 5 at arch/x86/events/intel/uncore.c:988 uncore_pci_remove+0xf1/0x110 ... CPU: 120 PID: 5 Comm: kworker/u1024:0 Not tainted 4.15.0-rc8 #1 Workqueue: kacpi_hotplug acpi_hotplug_work_fn ... Call Trace: pci_device_remove+0x36/0xb0 device_release_driver_internal+0x145/0x210 pci_stop_bus_device+0x76/0xa0 pci_stop_root_bus+0x44/0x60 acpi_pci_root_remove+0x1f/0x80 acpi_bus_trim+0x54/0x90 acpi_bus_trim+0x2e/0x90 acpi_device_hotplug+0x2bc/0x4b0 acpi_hotplug_work_fn+0x1a/0x30 process_one_work+0x141/0x340 worker_thread+0x47/0x3e0 kthread+0xf5/0x130 When uncore_pci_remove() runs, it tries to get the package ID to clear the value of uncore_extra_pci_dev[].dev[] by using topology_phys_to_logical_pkg(). The warning messesages are shown because topology_phys_to_logical_pkg() returns -1. arch/x86/events/intel/uncore.c: static void uncore_pci_remove(struct pci_dev *pdev) { ... phys_id = uncore_pcibus_to_physid(pdev->bus); ... pkg = topology_phys_to_logical_pkg(phys_id); // returns -1 for (i = 0; i < UNCORE_EXTRA_PCI_DEV_MAX; i++) { if (uncore_extra_pci_dev[pkg].dev[i] == pdev) { uncore_extra_pci_dev[pkg].dev[i] = NULL; break; } } WARN_ON_ONCE(i >= UNCORE_EXTRA_PCI_DEV_MAX); // <=========== HERE!! topology_phys_to_logical_pkg() tries to find cpuinfo_x86->phys_proc_id that matches the phys_pkg argument. arch/x86/kernel/smpboot.c: int topology_phys_to_logical_pkg(unsigned int phys_pkg) { int cpu; for_each_possible_cpu(cpu) { struct cpuinfo_x86 *c = &cpu_data(cpu); if (c->initialized && c->phys_proc_id == phys_pkg) return c->logical_proc_id; } return -1; } However, the phys_proc_id was already set to 0 by remove_siblinginfo() when the CPU was offlined. So, topology_phys_to_logical_pkg() cannot find the correct logical_proc_id and always returns -1. As the result, uncore_pci_remove() calls WARN_ON_ONCE() and the warning messages are shown. What is worse is that the bogus 'pkg' index results in two bugs: - We dereference uncore_extra_pci_dev[] with a negative index - We fail to clean up a stale pointer in uncore_extra_pci_dev[][] To fix these bugs, remove the clearing of ->phys_proc_id from remove_siblinginfo(). This should not cause any problems, because ->phys_proc_id is not used after it is hot-removed and it is re-set while hot-adding. Signed-off-by: Masayoshi Mizuma <m.miz...@jp.fujitsu.com> Acked-by: Thomas Gleixner <t...@linutronix.de> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: yasu.isim...@gmail.com Cc: <sta...@vger.kernel.org> Fixes: 30bb9811856f ("x86/topology: Avoid wasting 128k for package id array") Link: http://lkml.kernel.org/r/ed738d54-0f01-b38b-b794-c31dc118c...@gmail.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/kernel/smpboot.c | 1 - 1 file changed, 1 deletion(-) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 6f27facbaa9b..cfc61e1d45e2 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1430,7 +1430,6 @@ static void remove_siblinginfo(int cpu) cpumask_clear(cpu_llc_shared_mask(cpu)); cpumask_clear(topology_sibling_cpumask(cpu)); cpumask_clear(topology_core_cpumask(cpu)); - c->phys_proc_id = 0; c->cpu_core_id = 0; cpumask_clear_cpu(cpu, cpu_sibling_setup_mask); recompute_smt_state();