Index: sys/arm64/arm64/exception.S
===================================================================
--- sys/arm64/arm64/exception.S
+++ sys/arm64/arm64/exception.S
@@ -78,23 +78,25 @@
 
 	ldr	x0, [x18, #(PC_CURTHREAD)]
 	bl	dbg_monitor_enter
-	msr	daifclr, #DAIF_D	/* Enable the debug exception */
-.endif
+
+	/* Unmask debug and SError exceptions */
+	msr	daifclr, #(DAIF_D | DAIF_A)
+.else
 	/*
+	 * Unmask debug and SError exceptions.
 	 * For EL1, debug exceptions are conditionally unmasked in
 	 * do_el1h_sync().
 	 */
+	msr	daifclr, #(DAIF_A)
+.endif
 .endm
 
 .macro	restore_registers el
-.if \el == 1
 	/*
-	 * Disable interrupts and debug exceptions, x18 may change in the
-	 * interrupt exception handler.  For EL0 exceptions, do_ast already
-	 * did this.
+	 * Mask all exceptions, x18 may change in the interrupt exception
+	 * handler.
 	 */
-	msr	daifset, #(DAIF_D | DAIF_INTR)
-.endif
+	msr	daifset, #(DAIF_ALL)
 .if \el == 0
 	ldr	x0, [x18, #PC_CURTHREAD]
 	mov	x1, sp
@@ -153,8 +155,10 @@
 	/* Make sure the IRQs are enabled before calling ast() */
 	bic	x19, x19, #PSR_I
 1:
-	/* Disable interrupts */
-	msr	daifset, #(DAIF_D | DAIF_INTR)
+	/*
+	 * Mask interrupts while checking the ast pending flag
+	 */
+	msr	daifset, #(DAIF_INTR)
 
 	/* Read the current thread flags */
 	ldr	x1, [x18, #PC_CURTHREAD]	/* Load curthread */
Index: sys/arm64/arm64/machdep.c
===================================================================
--- sys/arm64/arm64/machdep.c
+++ sys/arm64/arm64/machdep.c
@@ -935,6 +935,12 @@
 	thread0.td_frame = &proc0_tf;
 	ptrauth_thread0(&thread0);
 	pcpup->pc_curpcb = thread0.td_pcb;
+
+	/*
+	 * Unmask SError exceptions. They are used to signal a RAS failure,
+	 * or other hardware error.
+	 */
+	serror_enable();
 }
 
 typedef struct {
Index: sys/arm64/arm64/vm_machdep.c
===================================================================
--- sys/arm64/arm64/vm_machdep.c
+++ sys/arm64/arm64/vm_machdep.c
@@ -114,7 +114,7 @@
 
 	/* Setup to release spin count in fork_exit(). */
 	td2->td_md.md_spinlock_count = 1;
-	td2->td_md.md_saved_daif = td1->td_md.md_saved_daif & ~DAIF_I_MASKED;
+	td2->td_md.md_saved_daif = PSR_DAIF_DEFAULT;
 }
 
 void
@@ -188,7 +188,7 @@
 
 	/* Setup to release spin count in fork_exit(). */
 	td->td_md.md_spinlock_count = 1;
-	td->td_md.md_saved_daif = td0->td_md.md_saved_daif & ~DAIF_I_MASKED;
+	td->td_md.md_saved_daif = PSR_DAIF_DEFAULT;
 
 	/* Generate new pointer authentication keys. */
 	ptrauth_copy_thread(td, td0);
Index: sys/arm64/include/armreg.h
===================================================================
--- sys/arm64/include/armreg.h
+++ sys/arm64/include/armreg.h
@@ -124,12 +124,6 @@
 #define	CTR_ILINE_VAL(reg)	((reg) & CTR_ILINE_MASK)
 #define	CTR_ILINE_SIZE(reg)	(4 << (CTR_ILINE_VAL(reg) >> CTR_ILINE_SHIFT))
 
-/* DAIF - Interrupt Mask Bits */
-#define	DAIF_D_MASKED		(1 << 9)
-#define	DAIF_A_MASKED		(1 << 8)
-#define	DAIF_I_MASKED		(1 << 7)
-#define	DAIF_F_MASKED		(1 << 6)
-
 /* DAIFSet/DAIFClear */
 #define	DAIF_D			(1 << 3)
 #define	DAIF_A			(1 << 2)
@@ -1079,6 +1073,8 @@
 #define	PSR_A		0x00000100
 #define	PSR_D		0x00000200
 #define	PSR_DAIF	(PSR_D | PSR_A | PSR_I | PSR_F)
+/* The default DAIF mask. These bits are valid in spsr_el1 and daif */
+#define	PSR_DAIF_DEFAULT (PSR_F)
 #define	PSR_IL		0x00100000
 #define	PSR_SS		0x00200000
 #define	PSR_V		0x10000000
Index: sys/arm64/include/cpufunc.h
===================================================================
--- sys/arm64/include/cpufunc.h
+++ sys/arm64/include/cpufunc.h
@@ -147,6 +147,13 @@
 	__asm __volatile("msr daifclr, #(" __XSTRING(DAIF_INTR) ")");
 }
 
+static __inline void
+serror_enable(void)
+{
+
+	__asm __volatile("msr daifclr, #(" __XSTRING(DAIF_A) ")");
+}
+
 static __inline register_t
 get_midr(void)
 {