On Fri, 25 Jun 2021 at 20:26, Chen-Yu Tsai <w...@kernel.org> wrote: > > 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.
Thanks for testing this feature. -Sumit _______________________________________________ Kgdb-bugreport mailing list Kgdb-bugreport@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kgdb-bugreport
