Messages in this thread | | | Date | Wed, 12 Jan 2022 14:31:08 -0500 | From | Masayoshi Mizuma <> | Subject | Re: [PATCH v7 0/7] arm64: Add framework to turn an IPI as NMI |
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On Wed, Jul 07, 2021 at 11:29:29AM +0530, Sumit Garg wrote: > On Fri, 25 Jun 2021 at 20:26, Chen-Yu Tsai <wens@kernel.org> wrote: > > > > On Mon, Nov 2, 2020 at 7:46 PM Sumit Garg <sumit.garg@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 <wens@csie.org> > > > > on an ROC-RK3399-PC. > > Thanks for testing this feature. > > -Sumit
Hello Sumit,
How is this patch series going?
- Masa
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