arm64: sdei: abort running SDEI handlers during crash

commit 5cd474e57368f0957c343bb21e309cf82826b1ef upstream.

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: f5df26961853 ("arm64: kernel: Add arch-specific SDEI entry code and CPU masking")
Signed-off-by: D Scott Phillips <scott@os.amperecomputing.com>
Cc: stable@vger.kernel.org
Reviewed-by: James Morse <james.morse@arm.com>
Tested-by: Mihai Carabas <mihai.carabas@oracle.com>
Link: https://lore.kernel.org/r/20230627002939.2758-1-scott@os.amperecomputing.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 38 insertions, 6 deletions

diff --git a/arch/arm64/include/asm/sdei.h b/arch/arm64/include/asm/sdei.h
index 4292d9bafb9d..484cb6972e99 100644
--- a/arch/arm64/include/asm/sdei.h
+++ b/arch/arm64/include/asm/sdei.h
@@ -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.
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 3671d9521d4f..beb4db21c89c 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -993,9 +993,13 @@ 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
 	/*
@@ -1062,6 +1066,14 @@ 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
@@ -1072,4 +1084,15 @@ 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 */
diff --git a/arch/arm64/kernel/sdei.c b/arch/arm64/kernel/sdei.c
index d56e170e1ca7..48c6457b67db 100644
--- a/arch/arm64/kernel/sdei.c
+++ b/arch/arm64/kernel/sdei.c
@@ -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;
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index ffc5d76cf695..d323621d14a5 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -1047,10 +1047,8 @@ 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);
@@ -1069,7 +1067,9 @@ 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)