Commit 5cd474e5 authored by D Scott Phillips's avatar D Scott Phillips Committed by Will Deacon
Browse files

arm64: sdei: abort running SDEI handlers during crash 



Interrupts are blocked in SDEI context, per the SDEI spec: "The client
interrupts cannot preempt the event handler." If we crashed in the SDEI
handler-running context (as with ACPI's AGDI) then we need to clean up the
SDEI state before proceeding to the crash kernel so that the crash kernel
can have working interrupts.

Track the active SDEI handler per-cpu so that we can COMPLETE_AND_RESUME
the handler, discarding the interrupted context.

Fixes: f5df2696 ("arm64: kernel: Add arch-specific SDEI entry code and CPU masking")
Signed-off-by: default avatarD Scott Phillips <scott@os.amperecomputing.com>
Cc: stable@vger.kernel.org
Reviewed-by: default avatarJames Morse <james.morse@arm.com>
Tested-by: default avatarMihai Carabas <mihai.carabas@oracle.com>
Link: https://lore.kernel.org/r/20230627002939.2758-1-scott@os.amperecomputing.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent b9d60124

arch/arm64/include/asm/sdei.h

+6 −0
Original line number Diff line number Diff line
@@ -17,6 +17,9 @@ 


#include <asm/virt.h>



DECLARE_PER_CPU(struct sdei_registered_event *, sdei_active_normal_event);

DECLARE_PER_CPU(struct sdei_registered_event *, sdei_active_critical_event);



extern unsigned long sdei_exit_mode;



/* Software Delegated Exception entry point from firmware*/
@@ -29,6 +32,9 @@ asmlinkage void __sdei_asm_entry_trampoline(unsigned long event_num, 
						   unsigned long pc,

						   unsigned long pstate);



/* Abort a running handler. Context is discarded. */

void __sdei_handler_abort(void);



/*

 * The above entry point does the minimum to call C code. This function does

 * anything else, before calling the driver.

arch/arm64/kernel/entry.S

+25 −2
Original line number Diff line number Diff line
@@ -986,9 +986,13 @@ SYM_CODE_START(__sdei_asm_handler) 


	mov	x19, x1



#if defined(CONFIG_VMAP_STACK) || defined(CONFIG_SHADOW_CALL_STACK)

	/* Store the registered-event for crash_smp_send_stop() */

	ldrb	w4, [x19, #SDEI_EVENT_PRIORITY]

#endif

	cbnz	w4, 1f

	adr_this_cpu dst=x5, sym=sdei_active_normal_event, tmp=x6

	b	2f

1:	adr_this_cpu dst=x5, sym=sdei_active_critical_event, tmp=x6

2:	str	x19, [x5]



#ifdef CONFIG_VMAP_STACK

	/*
@@ -1055,6 +1059,14 @@ SYM_CODE_START(__sdei_asm_handler) 


	ldr_l	x2, sdei_exit_mode



	/* Clear the registered-event seen by crash_smp_send_stop() */

	ldrb	w3, [x4, #SDEI_EVENT_PRIORITY]

	cbnz	w3, 1f

	adr_this_cpu dst=x5, sym=sdei_active_normal_event, tmp=x6

	b	2f

1:	adr_this_cpu dst=x5, sym=sdei_active_critical_event, tmp=x6

2:	str	xzr, [x5]



alternative_if_not ARM64_UNMAP_KERNEL_AT_EL0

	sdei_handler_exit exit_mode=x2

alternative_else_nop_endif
@@ -1065,4 +1077,15 @@ alternative_else_nop_endif 
#endif

SYM_CODE_END(__sdei_asm_handler)

NOKPROBE(__sdei_asm_handler)



SYM_CODE_START(__sdei_handler_abort)

	mov_q	x0, SDEI_1_0_FN_SDEI_EVENT_COMPLETE_AND_RESUME

	adr	x1, 1f

	ldr_l	x2, sdei_exit_mode

	sdei_handler_exit exit_mode=x2

	// exit the handler and jump to the next instruction.

	// Exit will stomp x0-x17, PSTATE, ELR_ELx, and SPSR_ELx.

1:	ret

SYM_CODE_END(__sdei_handler_abort)

NOKPROBE(__sdei_handler_abort)

#endif /* CONFIG_ARM_SDE_INTERFACE */

arch/arm64/kernel/sdei.c

+3 −0
Original line number Diff line number Diff line
@@ -47,6 +47,9 @@ DEFINE_PER_CPU(unsigned long *, sdei_shadow_call_stack_normal_ptr); 
DEFINE_PER_CPU(unsigned long *, sdei_shadow_call_stack_critical_ptr);

#endif



DEFINE_PER_CPU(struct sdei_registered_event *, sdei_active_normal_event);

DEFINE_PER_CPU(struct sdei_registered_event *, sdei_active_critical_event);



static void _free_sdei_stack(unsigned long * __percpu *ptr, int cpu)

{

	unsigned long *p;

arch/arm64/kernel/smp.c

+4 −4
Original line number Diff line number Diff line
@@ -1044,10 +1044,8 @@ void crash_smp_send_stop(void) 
	 * If this cpu is the only one alive at this point in time, online or

	 * not, there are no stop messages to be sent around, so just back out.

	 */

	if (num_other_online_cpus() == 0) {

		sdei_mask_local_cpu();

		return;

	}

	if (num_other_online_cpus() == 0)

		goto skip_ipi;



	cpumask_copy(&mask, cpu_online_mask);

	cpumask_clear_cpu(smp_processor_id(), &mask);
@@ -1066,7 +1064,9 @@ void crash_smp_send_stop(void) 
		pr_warn("SMP: failed to stop secondary CPUs %*pbl\n",

			cpumask_pr_args(&mask));



skip_ipi:

	sdei_mask_local_cpu();

	sdei_handler_abort();

}



bool smp_crash_stop_failed(void)

drivers/firmware/arm_sdei.c

+19 −0
Original line number Diff line number Diff line
@@ -1095,3 +1095,22 @@ int sdei_event_handler(struct pt_regs *regs, 
	return err;

}

NOKPROBE_SYMBOL(sdei_event_handler);



void sdei_handler_abort(void)

{

	/*

	 * If the crash happened in an SDEI event handler then we need to

	 * finish the handler with the firmware so that we can have working

	 * interrupts in the crash kernel.

	 */

	if (__this_cpu_read(sdei_active_critical_event)) {

	        pr_warn("still in SDEI critical event context, attempting to finish handler.\n");

	        __sdei_handler_abort();

	        __this_cpu_write(sdei_active_critical_event, NULL);

	}

	if (__this_cpu_read(sdei_active_normal_event)) {

	        pr_warn("still in SDEI normal event context, attempting to finish handler.\n");

	        __sdei_handler_abort();

	        __this_cpu_write(sdei_active_normal_event, NULL);

	}

}