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Mon, 02 Nov 2020 03:45:40 -0800 (PST) From: Sumit Garg To: maz@kernel.org, catalin.marinas@arm.com, will@kernel.org, daniel.thompson@linaro.org Subject: [PATCH v7 0/7] arm64: Add framework to turn an IPI as NMI Date: Mon, 2 Nov 2020 17:14:40 +0530 Message-Id: <1604317487-14543-1-git-send-email-sumit.garg@linaro.org> X-Mailer: git-send-email 2.7.4 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201102_064545_725958_6842F95C X-CRM114-Status: GOOD ( 19.60 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, Sumit Garg , tsbogend@alpha.franken.de, linux-kernel@vger.kernel.org, jason@lakedaemon.net, ito-yuichi@fujitsu.com, mpe@ellerman.id.au, x86@kernel.org, linux@armlinux.org.uk, dianders@chromium.org, mingo@redhat.com, bp@alien8.de, julien.thierry.kdev@gmail.com, jason.wessel@windriver.com, kgdb-bugreport@lists.sourceforge.net, tglx@linutronix.de, msys.mizuma@gmail.com, davem@davemloft.net, linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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) 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 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 arch/arm/include/asm/irq.h | 2 +- arch/arm/kernel/smp.c | 3 +- arch/arm64/include/asm/irq.h | 6 +++ arch/arm64/include/asm/nmi.h | 17 ++++++++ arch/arm64/kernel/Makefile | 2 +- arch/arm64/kernel/ipi_nmi.c | 84 ++++++++++++++++++++++++++++++++++++++++ arch/arm64/kernel/kgdb.c | 18 +++++++++ arch/arm64/kernel/smp.c | 8 ++++ arch/mips/include/asm/irq.h | 2 +- arch/mips/kernel/process.c | 3 +- arch/powerpc/include/asm/nmi.h | 2 +- arch/powerpc/kernel/stacktrace.c | 3 +- arch/sparc/include/asm/irq_64.h | 2 +- arch/sparc/kernel/process_64.c | 4 +- arch/x86/include/asm/irq.h | 2 +- arch/x86/kernel/apic/hw_nmi.c | 3 +- drivers/irqchip/irq-gic-v3.c | 29 ++++++++++---- include/linux/kgdb.h | 12 ++++++ include/linux/nmi.h | 12 ++---- kernel/debug/debug_core.c | 8 +++- 20 files changed, 194 insertions(+), 28 deletions(-) create mode 100644 arch/arm64/include/asm/nmi.h create mode 100644 arch/arm64/kernel/ipi_nmi.c -- 2.7.4 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel