Messages in this thread Patch in this message | | | Date | Wed, 10 Aug 2016 18:14:18 +0200 | From | Jiri Olsa <> | Subject | [PATCH] x86/smp: Fix __max_logical_packages value setup |
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On Wed, Aug 10, 2016 at 05:52:05PM +0200, Peter Zijlstra wrote: > On Wed, Aug 10, 2016 at 04:15:38PM +0200, Jiri Olsa wrote: > > it's very likely I'm missing something, but seems to me > > that attached patch (untested) might work as well > > Hmm, I think you're right. Earlier code (which hasn't survived) tried to > match logical and physical if possible, but that was busted and got > removed. > > The code as is should indeed allow for this. > > Maybe one nit, the variable is no longer used for a max, so maybe rename > it too?
ok, renaming it to logical_packages then, attaching full patch
thanks, jirka
--- Frank reported kernel panic when he disabled several cores in BIOS via following option:
Core Disable Bitmap(Hex) [0]
with number 0xFFE, which leaves 16 CPUs in system (out of 48).
The kernel panic below goes along with following messages:
smpboot: Max logical packages: 2^M smpboot: APIC(0) Converting physical 0 to logical package 0^M smpboot: APIC(20) Converting physical 1 to logical package 1^M smpboot: APIC(40) Package 2 exceeds logical package map^M smpboot: CPU 8 APICId 40 disabled^M smpboot: APIC(60) Package 3 exceeds logical package map^M smpboot: CPU 12 APICId 60 disabled^M ... general protection fault: 0000 [#1] SMP^M Modules linked in:^M CPU: 15 PID: 1 Comm: swapper/0 Not tainted 4.7.0-rc5+ #1^M Hardware name: SGI UV300/UV300, BIOS SGI UV 300 series BIOS 05/25/2016^M task: ffff8801673e0000 ti: ffff8801673ac000 task.ti: ffff8801673ac000^M RIP: 0010:[<ffffffff81014d54>] [<ffffffff81014d54>] uncore_change_context+0xd4/0x180^M ... [<ffffffff810158ac>] uncore_event_init_cpu+0x6c/0x70^M [<ffffffff81d8c91c>] intel_uncore_init+0x1c2/0x2dd^M [<ffffffff81d8c75a>] ? uncore_cpu_setup+0x17/0x17^M [<ffffffff81002190>] do_one_initcall+0x50/0x190^M [<ffffffff810ab193>] ? parse_args+0x293/0x480^M [<ffffffff81d87365>] kernel_init_freeable+0x1a5/0x249^M [<ffffffff81d86a35>] ? set_debug_rodata+0x12/0x12^M [<ffffffff816dc19e>] kernel_init+0xe/0x110^M [<ffffffff816e93bf>] ret_from_fork+0x1f/0x40^M [<ffffffff816dc190>] ? rest_init+0x80/0x80^M
The reason for the panic is wrong value of __max_logical_packages, which lets logical_package_map uninitialized and the uncore code relying on this map being properly initialized (maybe we should add some safety checks there as well).
The __max_logical_packages is computed as:
DIV_ROUND_UP(total_cpus, ncpus); - ncpus being number of cores
With above BIOS setup we get total_cpus == 16 which set __max_logical_packages to 2 (ncpus is 12).
Once topology_update_package_map processes CPU with logical pkg over 2 we display above messages and fail to initialize the physical_to_logical_pkg map, which makes the uncore code crash.
The fix is to remove logical_package_map bitmap completely and just keep and update the logical_packages number.
Reported-by: Frank Ramsay <framsay@redhat.com> Signed-off-by: Jiri Olsa <jolsa@kernel.org> --- arch/x86/include/asm/topology.h | 4 ++-- arch/x86/kernel/smpboot.c | 21 +++++---------------- 2 files changed, 7 insertions(+), 18 deletions(-)
diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h index cf75871d2f81..c28010088651 100644 --- a/arch/x86/include/asm/topology.h +++ b/arch/x86/include/asm/topology.h @@ -118,8 +118,8 @@ extern const struct cpumask *cpu_coregroup_mask(int cpu); #define topology_core_cpumask(cpu) (per_cpu(cpu_core_map, cpu)) #define topology_sibling_cpumask(cpu) (per_cpu(cpu_sibling_map, cpu)) -extern unsigned int __max_logical_packages; -#define topology_max_packages() (__max_logical_packages) +extern unsigned int logical_packages; +#define topology_max_packages() (logical_packages) extern int __max_smt_threads; diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 157bf0957219..b1b775dbede6 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -100,10 +100,9 @@ EXPORT_PER_CPU_SYMBOL(cpu_info); /* Logical package management. We might want to allocate that dynamically */ static int *physical_to_logical_pkg __read_mostly; static unsigned long *physical_package_map __read_mostly;; -static unsigned long *logical_package_map __read_mostly; static unsigned int max_physical_pkg_id __read_mostly; -unsigned int __max_logical_packages __read_mostly; -EXPORT_SYMBOL(__max_logical_packages); +unsigned int logical_packages __read_mostly; +EXPORT_SYMBOL(logical_packages); /* Maximum number of SMT threads on any online core */ int __max_smt_threads __read_mostly; @@ -277,14 +276,8 @@ int topology_update_package_map(unsigned int apicid, unsigned int cpu) if (test_and_set_bit(pkg, physical_package_map)) goto found; - new = find_first_zero_bit(logical_package_map, __max_logical_packages); - if (new >= __max_logical_packages) { - physical_to_logical_pkg[pkg] = -1; - pr_warn("APIC(%x) Package %u exceeds logical package map\n", - apicid, pkg); - return -ENOSPC; - } - set_bit(new, logical_package_map); + new = logical_packages++; + pr_info("APIC(%x) Converting physical %u to logical package %u\n", apicid, pkg, new); physical_to_logical_pkg[pkg] = new; @@ -340,7 +333,7 @@ static void __init smp_init_package_map(void) ncpus = 1; } - __max_logical_packages = DIV_ROUND_UP(total_cpus, ncpus); + logical_packages = 0; /* * Possibly larger than what we need as the number of apic ids per @@ -352,10 +345,6 @@ static void __init smp_init_package_map(void) memset(physical_to_logical_pkg, 0xff, size); size = BITS_TO_LONGS(max_physical_pkg_id) * sizeof(unsigned long); physical_package_map = kzalloc(size, GFP_KERNEL); - size = BITS_TO_LONGS(__max_logical_packages) * sizeof(unsigned long); - logical_package_map = kzalloc(size, GFP_KERNEL); - - pr_info("Max logical packages: %u\n", __max_logical_packages); for_each_present_cpu(cpu) { unsigned int apicid = apic->cpu_present_to_apicid(cpu); -- 2.4.11
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