kernel.git/arch/x86/kernel/smpboot.c, branch linux-3.17.y

sched: Fix unreleased llc_shared_mask bit during CPU hotplug

2014-09-24T13:13:20Z

The following bug can be triggered by hot adding and removing a large number of xen domain0's vcpus repeatedly: BUG: unable to handle kernel NULL pointer dereference at 0000000000000004 IP: [..] find_busiest_group PGD 5a9d5067 PUD 13067 PMD 0 Oops: 0000 [#3] SMP [...] Call Trace: load_balance ? _raw_spin_unlock_irqrestore idle_balance __schedule schedule schedule_timeout ? lock_timer_base schedule_timeout_uninterruptible msleep lock_device_hotplug_sysfs online_store dev_attr_store sysfs_write_file vfs_write SyS_write system_call_fastpath Last level cache shared mask is built during CPU up and the build_sched_domain() routine takes advantage of it to setup the sched domain CPU topology. However, llc_shared_mask is not released during CPU disable, which leads to an invalid sched domainCPU topology. This patch fix it by releasing the llc_shared_mask correctly during CPU disable. Yasuaki also reported that this can happen on real hardware: https://lkml.org/lkml/2014/7/22/1018 His case is here: == Here is an example on my system. My system has 4 sockets and each socket has 15 cores and HT is enabled. In this case, each core of sockes is numbered as follows: | CPU# Socket#0 | 0-14 , 60-74 Socket#1 | 15-29, 75-89 Socket#2 | 30-44, 90-104 Socket#3 | 45-59, 105-119 Then llc_shared_mask of CPU#30 has 0x3fff80000001fffc0000000. It means that last level cache of Socket#2 is shared with CPU#30-44 and 90-104. When hot-removing socket#2 and #3, each core of sockets is numbered as follows: | CPU# Socket#0 | 0-14 , 60-74 Socket#1 | 15-29, 75-89 But llc_shared_mask is not cleared. So llc_shared_mask of CPU#30 remains having 0x3fff80000001fffc0000000. After that, when hot-adding socket#2 and #3, each core of sockets is numbered as follows: | CPU# Socket#0 | 0-14 , 60-74 Socket#1 | 15-29, 75-89 Socket#2 | 30-59 Socket#3 | 90-119 Then llc_shared_mask of CPU#30 becomes 0x3fff8000fffffffc0000000. It means that last level cache of Socket#2 is shared with CPU#30-59 and 90-104. So the mask has the wrong value. Signed-off-by: Wanpeng Li Tested-by: Linn Crosetto Reviewed-by: Borislav Petkov Reviewed-by: Toshi Kani Reviewed-by: Yasuaki Ishimatsu Cc: Cc: David Rientjes Cc: Prarit Bhargava Cc: Steven Rostedt Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1411547885-48165-1-git-send-email-wanpeng.li@linux.intel.com Signed-off-by: Ingo Molnar

x86, apic: Remove setup_portio_remap callback

2014-07-31T15:05:44Z

Since commit b5660ba76b41 ("x86, platforms: Remove NUMAQ") removed NUMAQ, the setup_portio_remap() apic callback has been obsolete. Remove it. Signed-off-by: David Rientjes Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1407302351480.17503@chino.kir.corp.google.com Signed-off-by: H. Peter Anvin

x86, apic: Remove smp_callin_clear_local_apic callback

2014-07-31T15:05:41Z

Since commit b5660ba76b41 ("x86, platforms: Remove NUMAQ") removed NUMAQ, the smp_callin_clear_local_apic() apic callback has been obsolete. Remove it. Signed-off-by: David Rientjes Link: http://lkml.kernel.org/r/alpine.DEB.2.02.1407302349040.17503@chino.kir.corp.google.com Signed-off-by: H. Peter Anvin

Merge branch 'next' (accumulated 3.16 merge window patches) into master

2014-06-08T18:31:16Z

Now that 3.15 is released, this merges the 'next' branch into 'master', bringing us to the normal situation where my 'master' branch is the merge window. * accumulated work in next: (6809 commits) ufs: sb mutex merge + mutex_destroy powerpc: update comments for generic idle conversion cris: update comments for generic idle conversion idle: remove cpu_idle() forward declarations nbd: zero from and len fields in NBD_CMD_DISCONNECT. mm: convert some level-less printks to pr_* MAINTAINERS: adi-buildroot-devel is moderated MAINTAINERS: add linux-api for review of API/ABI changes mm/kmemleak-test.c: use pr_fmt for logging fs/dlm/debug_fs.c: replace seq_printf by seq_puts fs/dlm/lockspace.c: convert simple_str to kstr fs/dlm/config.c: convert simple_str to kstr mm: mark remap_file_pages() syscall as deprecated mm: memcontrol: remove unnecessary memcg argument from soft limit functions mm: memcontrol: clean up memcg zoneinfo lookup mm/memblock.c: call kmemleak directly from memblock_(alloc|free) mm/mempool.c: update the kmemleak stack trace for mempool allocations lib/radix-tree.c: update the kmemleak stack trace for radix tree allocations mm: introduce kmemleak_update_trace() mm/kmemleak.c: use %u to print ->checksum ...

Revert "x86/smpboot: Initialize secondary CPU only if master CPU will wait for it"

2014-06-08T17:09:49Z

This reverts commit 3e1a878b7ccdb31da6d9d2b855c72ad87afeba3f. It came in very late, and already has one reported failure: Sitsofe reports that the current tree fails to boot on his EeePC, and bisected it down to this. Rather than waste time trying to figure out what's wrong, just revert it. Reported-by: Sitsofe Wheeler Cc: Igor Mammedov Cc: Toshi Kani Cc: Thomas Gleixner Acked-by: Ingo Molnar Signed-off-by: Linus Torvalds

x86/smpboot: Initialize secondary CPU only if master CPU will wait for it

2014-06-05T14:33:08Z

Hang is observed on virtual machines during CPU hotplug, especially in big guests with many CPUs. (It reproducible more often if host is over-committed). It happens because master CPU gives up waiting on secondary CPU and allows it to run wild. As result AP causes locking or crashing system. For example as described here: https://lkml.org/lkml/2014/3/6/257 If master CPU have sent STARTUP IPI successfully, and AP signalled to master CPU that it's ready to start initialization, make master CPU wait indefinitely till AP is onlined. To ensure that AP won't ever run wild, make it wait at early startup till master CPU confirms its intention to wait for AP. If AP doesn't respond in 10 seconds, the master CPU will timeout and cancel AP onlining. Signed-off-by: Igor Mammedov Acked-by: Toshi Kani Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1401975765-22328-4-git-send-email-imammedo@redhat.com Signed-off-by: Ingo Molnar

x86/smpboot: Log error on secondary CPU wakeup failure at ERR level

2014-06-05T14:33:07Z

If system is running without debug level logging, it will not log error if do_boot_cpu() failed to wakeup AP. It may lead to silent AP bringup failures at boot time. Change message level to KERN_ERR to make error visible to user as it's done on other architectures. Signed-off-by: Igor Mammedov Acked-by: Toshi Kani Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1401975765-22328-3-git-send-email-imammedo@redhat.com Signed-off-by: Ingo Molnar

x86: Fix list/memory corruption on CPU hotplug

2014-06-05T14:33:07Z

currently if AP wake up is failed, master CPU marks AP as not present in do_boot_cpu() by calling set_cpu_present(cpu, false). That leads to following list corruption on the next physical CPU hotplug: [ 418.107336] WARNING: CPU: 1 PID: 45 at lib/list_debug.c:33 __list_add+0xbe/0xd0() [ 418.115268] list_add corruption. prev->next should be next (ffff88003dc57600), but was ffff88003e20c3a0. (prev=ffff88003e20c3a0). [ 418.123693] Modules linked in: nf_conntrack_netbios_ns nf_conntrack_broadcast ipt_MASQUERADE ip6t_REJECT ipt_REJECT cfg80211 xt_conntrack rfkill ee [ 418.138979] CPU: 1 PID: 45 Comm: kworker/u10:1 Not tainted 3.14.0-rc6+ #387 [ 418.149989] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2007 [ 418.165750] Workqueue: kacpi_hotplug acpi_hotplug_work_fn [ 418.166433] 0000000000000021 ffff880038ca7988 ffffffff8159b22d 0000000000000021 [ 418.176460] ffff880038ca79d8 ffff880038ca79c8 ffffffff8106942c ffff880038ca79e8 [ 418.177453] ffff88003e20c3a0 ffff88003dc57600 ffff88003e20c3a0 00000000ffffffea [ 418.178445] Call Trace: [ 418.185811] [] dump_stack+0x49/0x5c [ 418.186440] [] warn_slowpath_common+0x8c/0xc0 [ 418.187192] [] warn_slowpath_fmt+0x46/0x50 [ 418.191231] [] ? acpi_ns_get_node+0xb7/0xc7 [ 418.193889] [] __list_add+0xbe/0xd0 [ 418.196649] [] kobject_add_internal+0x79/0x200 [ 418.208610] [] kobject_add_varg+0x38/0x60 [ 418.213831] [] kobject_add+0x44/0x70 [ 418.229961] [] device_add+0xd0/0x550 [ 418.234991] [] ? pm_runtime_init+0xe5/0xf0 [ 418.250226] [] device_register+0x1e/0x30 [ 418.255296] [] register_cpu+0xe3/0x130 [ 418.266539] [] arch_register_cpu+0x65/0x150 [ 418.285845] [] acpi_processor_hotadd_init+0x5a/0x9b ... Which is caused by the fact that generic_processor_info() allocates logical CPU id by calling: cpu = cpumask_next_zero(-1, cpu_present_mask); which returns id of previously failed to wake up CPU, since its bit is cleared by do_boot_cpu() and as result register_cpu() tries to register another CPU with the same id as already present but failed to be onlined CPU. Taking in account that AP will not do anything if master CPU failed to wake it up, there is no reason to mark that AP as not present and break next cpu hotplug attempts. As a side effect of not marking AP as not present, user would be allowed to online it again later. Also fix memory corruption in acpi_unmap_lsapic() if during CPU hotplug master CPU failed to wake up AP it set percpu x86_cpu_to_apicid to BAD_APICID=0xFFFF for AP. However following attempt to unplug that CPU will lead to out of bound write access to __apicid_to_node[] which is 32768 items long on x86_64 kernel. So with above fix of cpu_present_mask make sure that a present CPU has a valid APIC ID by not setting x86_cpu_to_apicid to BAD_APICID in do_boot_cpu() on failure and allow acpi_processor_remove()->acpi_unmap_lsapic() cleanly remove CPU. Signed-off-by: Igor Mammedov Acked-by: Toshi Kani Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1401975765-22328-2-git-send-email-imammedo@redhat.com Signed-off-by: Ingo Molnar

x86, espfix: Make espfix64 a Kconfig option, fix UML

2014-05-04T17:00:49Z

Make espfix64 a hidden Kconfig option. This fixes the x86-64 UML build which had broken due to the non-existence of init_espfix_bsp() in UML: since UML uses its own Kconfig, this option does not appear in the UML build. This also makes it possible to make support for 16-bit segments a configuration option, for the people who want to minimize the size of the kernel. Reported-by: Ingo Molnar Signed-off-by: H. Peter Anvin Cc: Richard Weinberger Link: http://lkml.kernel.org/r/1398816946-3351-1-git-send-email-hpa@linux.intel.com

x86-64, espfix: Don't leak bits 31:16 of %esp returning to 16-bit stack

2014-04-30T21:14:28Z

The IRET instruction, when returning to a 16-bit segment, only restores the bottom 16 bits of the user space stack pointer. This causes some 16-bit software to break, but it also leaks kernel state to user space. We have a software workaround for that ("espfix") for the 32-bit kernel, but it relies on a nonzero stack segment base which is not available in 64-bit mode. In checkin: b3b42ac2cbae x86-64, modify_ldt: Ban 16-bit segments on 64-bit kernels we "solved" this by forbidding 16-bit segments on 64-bit kernels, with the logic that 16-bit support is crippled on 64-bit kernels anyway (no V86 support), but it turns out that people are doing stuff like running old Win16 binaries under Wine and expect it to work. This works around this by creating percpu "ministacks", each of which is mapped 2^16 times 64K apart. When we detect that the return SS is on the LDT, we copy the IRET frame to the ministack and use the relevant alias to return to userspace. The ministacks are mapped readonly, so if IRET faults we promote #GP to #DF which is an IST vector and thus has its own stack; we then do the fixup in the #DF handler. (Making #GP an IST exception would make the msr_safe functions unsafe in NMI/MC context, and quite possibly have other effects.) Special thanks to: - Andy Lutomirski, for the suggestion of using very small stack slots and copy (as opposed to map) the IRET frame there, and for the suggestion to mark them readonly and let the fault promote to #DF. - Konrad Wilk for paravirt fixup and testing. - Borislav Petkov for testing help and useful comments. Reported-by: Brian Gerst Signed-off-by: H. Peter Anvin Link: http://lkml.kernel.org/r/1398816946-3351-1-git-send-email-hpa@linux.intel.com Cc: Konrad Rzeszutek Wilk Cc: Borislav Petkov Cc: Andrew Lutomriski Cc: Linus Torvalds Cc: Dirk Hohndel Cc: Arjan van de Ven Cc: comex Cc: Alexander van Heukelum Cc: Boris Ostrovsky Cc: # consider after upstream merge