[PATCH v2 RESEND 1/2] arm64: sdei: Use alternative patching to select the conduit in sdei exit

[PATCH v2 RESEND 1/2] arm64: sdei: Use alternative patching to select the conduit in sdei exit

[D Scott Phillips]

Patch in the conduit instruction for SDEI instead of branching between the
possible conduits. The sdei driver's conduit initialization is moved
earlier in the initialization flow, into setup_arch(), so that it is ready
in time for alternative patching.

Suggested-by: James Morse <james.morse@arm.com>
Signed-off-by: D Scott Phillips <scott@os.amperecomputing.com>
---
 arch/arm64/include/asm/sdei.h | 13 +++----
 arch/arm64/kernel/entry.S     | 26 ++++++-------
 arch/arm64/kernel/sdei.c      | 30 ++++++++++++---
 arch/arm64/kernel/setup.c     |  3 ++
 drivers/firmware/arm_sdei.c   | 71 +++++++++++++++++++----------------
 include/linux/arm_sdei.h      |  6 ++-
 6 files changed, 88 insertions(+), 61 deletions(-)

diff --git a/arch/arm64/include/asm/sdei.h b/arch/arm64/include/asm/sdei.h
index 4292d9bafb9d..badb39510515 100644
--- a/arch/arm64/include/asm/sdei.h
+++ b/arch/arm64/include/asm/sdei.h
@@ -3,10 +3,6 @@
 #ifndef __ASM_SDEI_H
 #define __ASM_SDEI_H
 
-/* Values for sdei_exit_mode */
-#define SDEI_EXIT_HVC  0
-#define SDEI_EXIT_SMC  1
-
 #define SDEI_STACK_SIZE		IRQ_STACK_SIZE
 
 #ifndef __ASSEMBLY__
@@ -17,8 +13,6 @@
 
 #include <asm/virt.h>
 
-extern unsigned long sdei_exit_mode;
-
 /* Software Delegated Exception entry point from firmware*/
 asmlinkage void __sdei_asm_handler(unsigned long event_num, unsigned long arg,
 				   unsigned long pc, unsigned long pstate);
@@ -40,8 +34,11 @@ asmlinkage unsigned long __sdei_handler(struct pt_regs *regs,
 unsigned long do_sdei_event(struct pt_regs *regs,
 			    struct sdei_registered_event *arg);
 
-unsigned long sdei_arch_get_entry_point(int conduit);
-#define sdei_arch_get_entry_point(x)	sdei_arch_get_entry_point(x)
+unsigned long sdei_arch_get_entry_point(void);
+#define sdei_arch_get_entry_point	sdei_arch_get_entry_point
+
+void __init sdei_patch_conduit(struct alt_instr *alt, __le32 *origptr,
+			       __le32 *updptr, int nr_inst);
 
 #endif /* __ASSEMBLY__ */
 #endif	/* __ASM_SDEI_H */
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index ab2a6e33c052..ae7aa02f0df5 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -914,13 +914,10 @@ NOKPROBE(call_on_irq_stack)
 #include <asm/sdei.h>
 #include <uapi/linux/arm_sdei.h>
 
-.macro sdei_handler_exit exit_mode
-	/* On success, this call never returns... */
-	cmp	\exit_mode, #SDEI_EXIT_SMC
-	b.ne	99f
-	smc	#0
-	b	.
-99:	hvc	#0
+.macro sdei_handler_exit
+alternative_cb	ARM64_ALWAYS_SYSTEM, sdei_patch_conduit
+	nop	// Patched to SMC/HVC #0
+alternative_cb_end
 	b	.
 .endm
 
@@ -955,7 +952,6 @@ NOKPROBE(__sdei_asm_entry_trampoline)
  * Make the exit call and restore the original ttbr1_el1
  *
  * x0 & x1: setup for the exit API call
- * x2: exit_mode
  * x4: struct sdei_registered_event argument from registration time.
  */
 SYM_CODE_START(__sdei_asm_exit_trampoline)
@@ -964,7 +960,7 @@ SYM_CODE_START(__sdei_asm_exit_trampoline)
 
 	tramp_unmap_kernel	tmp=x4
 
-1:	sdei_handler_exit exit_mode=x2
+1:	sdei_handler_exit
 SYM_CODE_END(__sdei_asm_exit_trampoline)
 NOKPROBE(__sdei_asm_exit_trampoline)
 .popsection		// .entry.tramp.text
@@ -1070,14 +1066,16 @@ SYM_CODE_START(__sdei_asm_handler)
 	mov_q	x3, SDEI_1_0_FN_SDEI_EVENT_COMPLETE_AND_RESUME
 	csel	x0, x2, x3, ls
 
-	ldr_l	x2, sdei_exit_mode
-
-alternative_if_not ARM64_UNMAP_KERNEL_AT_EL0
-	sdei_handler_exit exit_mode=x2
+#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
+alternative_if ARM64_UNMAP_KERNEL_AT_EL0
+	b 1f
 alternative_else_nop_endif
+#endif
+
+	sdei_handler_exit
 
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
-	tramp_alias	dst=x5, sym=__sdei_asm_exit_trampoline, tmp=x3
+1:	tramp_alias	dst=x5, sym=__sdei_asm_exit_trampoline, tmp=x3
 	br	x5
 #endif
 SYM_CODE_END(__sdei_asm_handler)
diff --git a/arch/arm64/kernel/sdei.c b/arch/arm64/kernel/sdei.c
index 830be01af32d..be7f6ea49956 100644
--- a/arch/arm64/kernel/sdei.c
+++ b/arch/arm64/kernel/sdei.c
@@ -20,8 +20,6 @@
 #include <asm/sysreg.h>
 #include <asm/vmap_stack.h>
 
-unsigned long sdei_exit_mode;
-
 /*
  * VMAP'd stacks checking for stack overflow on exception using sp as a scratch
  * register, meaning SDEI has to switch to its own stack. We need two stacks as
@@ -162,7 +160,7 @@ static int init_sdei_scs(void)
 	return err;
 }
 
-unsigned long sdei_arch_get_entry_point(int conduit)
+unsigned long sdei_arch_get_entry_point(void)
 {
 	/*
 	 * SDEI works between adjacent exception levels. If we booted at EL1 we
@@ -181,8 +179,6 @@ unsigned long sdei_arch_get_entry_point(int conduit)
 	if (init_sdei_scs())
 		goto out_err_free_stacks;
 
-	sdei_exit_mode = (conduit == SMCCC_CONDUIT_HVC) ? SDEI_EXIT_HVC : SDEI_EXIT_SMC;
-
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
 	if (arm64_kernel_unmapped_at_el0()) {
 		unsigned long offset;
@@ -262,3 +258,27 @@ unsigned long __kprobes do_sdei_event(struct pt_regs *regs,
 
 	return vbar + 0x480;
 }
+
+/*
+ * Patch in the sdei conduit instruction.
+ */
+void __init sdei_patch_conduit(struct alt_instr *alt, __le32 *origptr,
+			       __le32 *updptr, int nr_inst)
+{
+	u32 insn;
+
+	BUG_ON(nr_inst != 1); /* NOP -> HVC/SMC */
+
+	switch (sdei_get_conduit()) {
+	case SMCCC_CONDUIT_HVC:
+		insn = aarch64_insn_get_hvc_value();
+		break;
+	case SMCCC_CONDUIT_SMC:
+		insn = aarch64_insn_get_smc_value();
+		break;
+	default:
+		return;
+	}
+
+	*updptr = cpu_to_le32(insn);
+}
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index b8ec7b3ac9cb..6286c4c59074 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -7,6 +7,7 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/arm_sdei.h>
 #include <linux/export.h>
 #include <linux/kernel.h>
 #include <linux/stddef.h>
@@ -365,6 +366,8 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
 	else
 		psci_acpi_init();
 
+	sdei_conduit_init();
+
 	init_bootcpu_ops();
 	smp_init_cpus();
 	smp_build_mpidr_hash();
diff --git a/drivers/firmware/arm_sdei.c b/drivers/firmware/arm_sdei.c
index 1e1a51510e83..0dbb88bcc9a2 100644
--- a/drivers/firmware/arm_sdei.c
+++ b/drivers/firmware/arm_sdei.c
@@ -919,37 +919,12 @@ int sdei_unregister_ghes(struct ghes *ghes)
 	return err;
 }
 
-static int sdei_get_conduit(struct platform_device *pdev)
+enum arm_smccc_conduit sdei_get_conduit(void)
 {
-	const char *method;
-	struct device_node *np = pdev->dev.of_node;
-
-	sdei_firmware_call = NULL;
-	if (np) {
-		if (of_property_read_string(np, "method", &method)) {
-			pr_warn("missing \"method\" property\n");
-			return SMCCC_CONDUIT_NONE;
-		}
-
-		if (!strcmp("hvc", method)) {
-			sdei_firmware_call = &sdei_smccc_hvc;
-			return SMCCC_CONDUIT_HVC;
-		} else if (!strcmp("smc", method)) {
-			sdei_firmware_call = &sdei_smccc_smc;
-			return SMCCC_CONDUIT_SMC;
-		}
-
-		pr_warn("invalid \"method\" property: %s\n", method);
-	} else if (!acpi_disabled) {
-		if (acpi_psci_use_hvc()) {
-			sdei_firmware_call = &sdei_smccc_hvc;
-			return SMCCC_CONDUIT_HVC;
-		} else {
-			sdei_firmware_call = &sdei_smccc_smc;
-			return SMCCC_CONDUIT_SMC;
-		}
-	}
-
+	if (sdei_firmware_call == sdei_smccc_hvc)
+		return SMCCC_CONDUIT_HVC;
+	if (sdei_firmware_call == sdei_smccc_smc)
+		return SMCCC_CONDUIT_SMC;
 	return SMCCC_CONDUIT_NONE;
 }
 
@@ -957,9 +932,7 @@ static int sdei_probe(struct platform_device *pdev)
 {
 	int err;
 	u64 ver = 0;
-	int conduit;
 
-	conduit = sdei_get_conduit(pdev);
 	if (!sdei_firmware_call)
 		return 0;
 
@@ -984,7 +957,7 @@ static int sdei_probe(struct platform_device *pdev)
 	if (err)
 		return err;
 
-	sdei_entry_point = sdei_arch_get_entry_point(conduit);
+	sdei_entry_point = sdei_arch_get_entry_point();
 	if (!sdei_entry_point) {
 		/* Not supported due to hardware or boot configuration */
 		sdei_mark_interface_broken();
@@ -1059,6 +1032,38 @@ static bool __init sdei_present_acpi(void)
 	return true;
 }
 
+void __init sdei_conduit_init(void)
+{
+	const char *method;
+	struct device_node *np;
+
+	if (acpi_disabled) {
+		np = of_find_matching_node_and_match(NULL, sdei_of_match, NULL);
+		if (!np || !of_device_is_available(np))
+			return;
+
+		if (of_property_read_string(np, "method", &method)) {
+			pr_warn("missing \"method\" property\n");
+			return;
+		}
+
+		if (!strcmp("hvc", method))
+			sdei_firmware_call = &sdei_smccc_hvc;
+		else if (!strcmp("smc", method))
+			sdei_firmware_call = &sdei_smccc_smc;
+		else
+			pr_warn("invalid \"method\" property: %s\n", method);
+	} else {
+		if (!sdei_present_acpi())
+			return;
+
+		if (acpi_psci_use_hvc())
+			sdei_firmware_call = &sdei_smccc_hvc;
+		else
+			sdei_firmware_call = &sdei_smccc_smc;
+	}
+}
+
 void __init sdei_init(void)
 {
 	struct platform_device *pdev;
diff --git a/include/linux/arm_sdei.h b/include/linux/arm_sdei.h
index 14dc461b0e82..de9aafd87c48 100644
--- a/include/linux/arm_sdei.h
+++ b/include/linux/arm_sdei.h
@@ -13,7 +13,7 @@
 
 /* Arch code should override this to set the entry point from firmware... */
 #ifndef sdei_arch_get_entry_point
-#define sdei_arch_get_entry_point(conduit)	(0)
+#define sdei_arch_get_entry_point()	(0)
 #endif
 
 /*
@@ -22,6 +22,8 @@
  */
 typedef int (sdei_event_callback)(u32 event, struct pt_regs *regs, void *arg);
 
+enum arm_smccc_conduit sdei_get_conduit(void);
+
 /*
  * Register your callback to claim an event. The event must be described
  * by firmware.
@@ -47,10 +49,12 @@ int sdei_unregister_ghes(struct ghes *ghes);
 int sdei_mask_local_cpu(void);
 int sdei_unmask_local_cpu(void);
 void __init sdei_init(void);
+void __init sdei_conduit_init(void);
 #else
 static inline int sdei_mask_local_cpu(void) { return 0; }
 static inline int sdei_unmask_local_cpu(void) { return 0; }
 static inline void sdei_init(void) { }
+static inline void sdei_conduit_init(void) { }
 #endif /* CONFIG_ARM_SDE_INTERFACE */
 
 
-- 
2.39.2

[PATCH v2 RESEND 2/2] arm64: sdei: abort running SDEI handlers during crash

[D Scott Phillips]

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>
---
 arch/arm64/include/asm/sdei.h |  8 ++++++++
 arch/arm64/kernel/entry.S     | 24 ++++++++++++++++++++++++
 arch/arm64/kernel/sdei.c      |  3 +++
 arch/arm64/kernel/smp.c       | 27 +++++++++++++++++++++++----
 4 files changed, 58 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/sdei.h b/arch/arm64/include/asm/sdei.h
index badb39510515..58bc9ebe4a6d 100644
--- a/arch/arm64/include/asm/sdei.h
+++ b/arch/arm64/include/asm/sdei.h
@@ -13,6 +13,11 @@
 
 #include <asm/virt.h>
 
+#ifdef CONFIG_ARM_SDE_INTERFACE
+DECLARE_PER_CPU(struct sdei_registered_event *, sdei_active_normal_event);
+DECLARE_PER_CPU(struct sdei_registered_event *, sdei_active_critical_event);
+#endif
+
 /* Software Delegated Exception entry point from firmware*/
 asmlinkage void __sdei_asm_handler(unsigned long event_num, unsigned long arg,
 				   unsigned long pc, unsigned long pstate);
@@ -23,6 +28,9 @@ 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 ae7aa02f0df5..6d5694dfcb7b 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -1003,6 +1003,12 @@ SYM_CODE_START(__sdei_asm_handler)
 	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
 	/*
 	 * entry.S may have been using sp as a scratch register, find whether
@@ -1066,6 +1072,13 @@ SYM_CODE_START(__sdei_asm_handler)
 	mov_q	x3, SDEI_1_0_FN_SDEI_EVENT_COMPLETE_AND_RESUME
 	csel	x0, x2, x3, ls
 
+	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]
+
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
 alternative_if ARM64_UNMAP_KERNEL_AT_EL0
 	b 1f
@@ -1080,4 +1093,15 @@ 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
+	sdei_handler_exit
+	// 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 be7f6ea49956..07fa9630f0ce 100644
--- a/arch/arm64/kernel/sdei.c
+++ b/arch/arm64/kernel/sdei.c
@@ -45,6 +45,9 @@ 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 4e8327264255..ea221b1ee9ac 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 +1067,28 @@ 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();
+
+#ifdef CONFIG_ARM_SDE_INTERFACE
+	/*
+	 * 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("SMP: stopped CPUS from SDEI critical event handler "
+			"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("SMP: stopped CPUS from SDEI normal event handler "
+			"context, attempting to finish handler.\n");
+		sdei_handler_abort();
+		__this_cpu_write(sdei_active_normal_event, NULL);
+	}
+#endif
 }
 
 bool smp_crash_stop_failed(void)
-- 
2.39.2