On Mon, Nov 2, 2020 at 7:46 PM Sumit Garg <sumit.g...@linaro.org> wrote: > > With pseudo NMIs support available its possible to configure SGIs to be > triggered as pseudo NMIs running in NMI context. And kernel features > such as: > - NMI backtrace can leverage IPI turned as NMI to get a backtrace of CPU > stuck in hard lockup using magic SYSRQ. > - kgdb relies on NMI support to round up CPUs which are stuck in hard > lockup state with interrupts disabled. > > This patch-set adds framework to turn an IPI as NMI which can be triggered > as a pseudo NMI which in turn invokes registered NMI handlers. > > After this patch-set we should be able to get a backtrace for a CPU > stuck in HARDLOCKUP. Have a look at an examples below from a hard lockup > testcase run on Developerbox: > > $ echo HARDLOCKUP > /sys/kernel/debug/provoke-crash/DIRECT > > NMI backtrace: > ============== > > # Issue Magic SysRq to dump backtrace > > [ 376.894502] NMI backtrace for cpu 8 > [ 376.894506] CPU: 8 PID: 555 Comm: bash Not tainted > 5.9.0-rc3-00740-g06ff047-dirty #242 > [ 376.894510] Hardware name: Socionext SynQuacer E-series DeveloperBox, BIOS > build #73 Apr 6 2020 > [ 376.894514] pstate: 40000005 (nZcv daif -PAN -UAO BTYPE=--) > [ 376.894517] pc : lkdtm_HARDLOCKUP+0x8/0x18 > [ 376.894520] lr : lkdtm_do_action+0x24/0x30 > [ 376.894524] sp : ffff800012cebd20 > [ 376.894527] pmr_save: 00000060 > [ 376.894530] x29: ffff800012cebd20 x28: ffff000875ae8000 > [ 376.894540] x27: 0000000000000000 x26: 0000000000000000 > [ 376.894550] x25: 000000000000001a x24: ffff800012cebe40 > [ 376.894560] x23: 000000000000000b x22: ffff800010fc5040 > [ 376.894569] x21: ffff000878b61000 x20: ffff8000113b2870 > [ 376.894579] x19: 000000000000001b x18: 0000000000000010 > [ 376.894588] x17: 0000000000000000 x16: 0000000000000000 > [ 376.894598] x15: ffff000875ae8470 x14: 00000000000002ad > [ 376.894613] x13: 0000000000000000 x12: 0000000000000000 > [ 376.894622] x11: 0000000000000007 x10: 00000000000009c0 > [ 376.894631] x9 : ffff800012ceba80 x8 : ffff000875ae8a20 > [ 376.894641] x7 : ffff00087f6b3280 x6 : ffff00087f6b3200 > [ 376.894651] x5 : 0000000000000000 x4 : ffff00087f6a91f8 > [ 376.894660] x3 : ffff00087f6b0120 x2 : 1aa310cec69eb500 > [ 376.894670] x1 : 0000000000000000 x0 : 0000000000000060 > [ 376.894679] Call trace: > [ 376.894683] lkdtm_HARDLOCKUP+0x8/0x18 > [ 376.894686] direct_entry+0x124/0x1c0 > [ 376.894689] full_proxy_write+0x60/0xb0 > [ 376.894693] vfs_write+0xf0/0x230 > [ 376.894696] ksys_write+0x6c/0xf8 > [ 376.894699] __arm64_sys_write+0x1c/0x28 > [ 376.894703] el0_svc_common.constprop.0+0x74/0x1f0 > [ 376.894707] do_el0_svc+0x24/0x90 > [ 376.894710] el0_sync_handler+0x180/0x2f8 > [ 376.894713] el0_sync+0x158/0x180 > > KGDB: > ===== > > # Enter kdb via Magic SysRq > > [6]kdb> btc > btc: cpu status: Currently on cpu 6 > Available cpus: 0-5(I), 6, 7(I), 8, 9-23(I) > <snip> > Stack traceback for pid 555 > 0xffff000875ae8000 555 554 1 8 R 0xffff000875ae89c0 bash > CPU: 8 PID: 555 Comm: bash Not tainted 5.9.0-rc3-00740-g06ff047-dirty #242 > Hardware name: Socionext SynQuacer E-series DeveloperBox, BIOS build #73 Apr > 6 2020 > Call trace: > dump_backtrace+0x0/0x1a0 > show_stack+0x18/0x28 > dump_stack+0xc0/0x11c > kgdb_cpu_enter+0x648/0x660 > kgdb_nmicallback+0xa0/0xa8 > ipi_kgdb_nmicallback+0x24/0x30 > ipi_nmi_handler+0x48/0x60 > handle_percpu_devid_fasteoi_ipi+0x74/0x88 > generic_handle_irq+0x30/0x48 > handle_domain_nmi+0x48/0x80 > gic_handle_irq+0x18c/0x34c > el1_irq+0xcc/0x180 > lkdtm_HARDLOCKUP+0x8/0x18 > direct_entry+0x124/0x1c0 > full_proxy_write+0x60/0xb0 > vfs_write+0xf0/0x230 > ksys_write+0x6c/0xf8 > __arm64_sys_write+0x1c/0x28 > el0_svc_common.constprop.0+0x74/0x1f0 > do_el0_svc+0x24/0x90 > el0_sync_handler+0x180/0x2f8 > el0_sync+0x158/0x180 > <snip> > > Changes in v7: > - Add a new library function: kgdb_smp_call_nmi_hook() to expose fallback > mechanism to arch specific code. > - Addressed other misc comments from Daniel. > > Changes in v6: > - Two new patches: #4 and #6 which adds runtime fallback framework for > sysrq backtrace and kgdb roundup features. > - Reversed order of NMI backtrace and kgdb roundup feaure patches. > - Addressed other misc. comments from Marc. > - I haven't picked any tags from v5 since I think there is major rework > involved. Masayoshi, could you please confirm if these features still > work for you? > > Changes in v5: > - Rebased to head of upstream master. > - Remove redundant invocation of ipi_nmi_setup(). > - Addressed misc. comments. > > Changes in v4: > - Move IPI NMI framework to a separate file. > - Get rid of hard-coded IPI_CALL_NMI_FUNC allocation. > - Add NMI backtrace support leveraged via magic SYSRQ. > > Changes in v3: > - Rebased to Marc's latest IPIs patch-set [1]. > > [1] https://lkml.org/lkml/2020/9/1/603 > > Changes since RFC version [1]: > - Switch to use generic interrupt framework to turn an IPI as NMI. > - Dependent on Marc's patch-set [2] which turns IPIs into normal > interrupts. > - Addressed misc. comments from Doug on patch #4. > - Posted kgdb NMI printk() fixup separately which has evolved since > to be solved using different approach via changing kgdb interception > of printk() in common printk() code (see patch [3]). > > [1] https://lkml.org/lkml/2020/4/24/328 > [2] https://lkml.org/lkml/2020/5/19/710 > [3] https://lkml.org/lkml/2020/5/20/418 > > Sumit Garg (7): > arm64: Add framework to turn IPI as NMI > irqchip/gic-v3: Enable support for SGIs to act as NMIs > arm64: smp: Assign and setup an IPI as NMI > nmi: backtrace: Allow runtime arch specific override > arm64: ipi_nmi: Add support for NMI backtrace > kgdb: Expose default CPUs roundup fallback mechanism > arm64: kgdb: Roundup cpus using IPI as NMI
Tested-by: Chen-Yu Tsai <w...@csie.org> on an ROC-RK3399-PC. _______________________________________________ Kgdb-bugreport mailing list Kgdb-bugreport@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kgdb-bugreport
