On 08/15/2016 06:17 AM, Jiri Olsa wrote: > On Mon, Aug 15, 2016 at 11:04:34AM +0200, Peter Zijlstra wrote: >> On Fri, Aug 12, 2016 at 02:24:57PM +0200, Jiri Olsa wrote: >>> I still need to test this, but would this be something >>> like you proposed on irc? >> >> Yep, looks good. Please post with Changelog etc.. > > attached, > > 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 keep and update the logical_packages number instead. > > After we enumerate all the present cpus, we check if the > enumerated logical packages count is within its computed > maximum from BIOS data. > > If it's not the case, we set this maximum to the new enumerated > value and freeze any new addition of logical packages. > > The freeze is because lot of init code like uncore/rapl/cqm > depends on having maximum logical package value set to allocate > their data, so we can't change it later on. > > Suggested-by: Peter Zijlstra <[email protected]> > Reported-by: Frank Ramsay <[email protected]> > Signed-off-by: Jiri Olsa <[email protected]>
Reviewed-and-tested-by: Prarit Bhargava <[email protected]> >From dmidecode: Core Count: 24 Core Enabled: 24 Thread Count: 48 Testing of patch below ... Orig kernel output: [ 0.464981] smpboot: Max logical packages: 19 [ 0.469861] smpboot: APIC(0) Converting physical 0 to logical package 0 [ 0.477261] smpboot: APIC(40) Converting physical 1 to logical package 1 [ 0.484760] smpboot: APIC(80) Converting physical 2 to logical package 2 [ 0.492258] smpboot: APIC(c0) Converting physical 3 to logical package 3 1. nr_cpus=8, should stop enumerating in package 0 [ 0.533664] smpboot: APIC(0) Converting physical 0 to logical package 0 [ 0.539596] smpboot: Max logical packages: 19 2. max_cpus=8, should still enumerate all packages [ 0.526494] smpboot: APIC(0) Converting physical 0 to logical package 0 [ 0.532428] smpboot: APIC(40) Converting physical 1 to logical package 1 [ 0.538456] smpboot: APIC(80) Converting physical 2 to logical package 2 [ 0.544486] smpboot: APIC(c0) Converting physical 3 to logical package 3 [ 0.550524] smpboot: Max logical packages: 19 3. nr_cpus=49 ( 2 socket + 1 core on 3rd socket), should stop enumerating in package 2 [ 0.521378] smpboot: APIC(0) Converting physical 0 to logical package 0 [ 0.527314] smpboot: APIC(40) Converting physical 1 to logical package 1 [ 0.533345] smpboot: APIC(80) Converting physical 2 to logical package 2 [ 0.539368] smpboot: Max logical packages: 19 4. maxcpus=49, should still enumerate all packages [ 0.525591] smpboot: APIC(0) Converting physical 0 to logical package 0 [ 0.531525] smpboot: APIC(40) Converting physical 1 to logical package 1 [ 0.537547] smpboot: APIC(80) Converting physical 2 to logical package 2 [ 0.543579] smpboot: APIC(c0) Converting physical 3 to logical package 3 [ 0.549624] smpboot: Max logical packages: 19 5. kdump (nr_cpus=1) works. P.
