x86: mask all LAPIC vectors early, before BSP interrupts are enabled

If APIC is left in somewhat bad state, with some source hot (not masked
and active, e.g. timers after kexec or due to BIOS bug), we get the
interrupt too early.

Reported by:	jmg
Reviewed by:	markj
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D54543

sys/x86/x86/local_apic.c

@@ -428,6 +428,7 @@ lapic_is_x2apic(void)
 	    (APICBASE_X2APIC | APICBASE_ENABLED));
 }
 
+static void	lapic_early_mask_vecs(void);
 static void	lapic_enable(void);
 static void	lapic_resume(struct pic *pic, bool suspend_cancelled);
 static void	lapic_timer_oneshot(struct lapic *);
@@ -553,6 +554,7 @@ lapic_init(vm_paddr_t addr)
 
 	/* Perform basic initialization of the BSP's local APIC. */
 	lapic_enable();
+	lapic_early_mask_vecs();
 
 	/* Set BSP's per-CPU local APIC ID. */
 	PCPU_SET(apic_id, lapic_id());
@@ -791,6 +793,32 @@ lapic_xapic_mode(void)
 	intr_restore(saveintr);
 }
 
+static void
+lapic_early_mask_vec(const struct lvt *l)
+{
+	uint32_t v;
+
+	if (l->lvt_masked != 0) {
+		v = lapic_read32(l->lvt_reg);
+		v |= APIC_LVT_M;
+		lapic_write32(l->lvt_reg, v);
+	}
+}
+
+/* Done on BSP only */
+static void
+lapic_early_mask_vecs(void)
+{
+	int elvt_count, i;
+
+	for (i = 0; i < APIC_LVT_MAX; i++)
+		lapic_early_mask_vec(&lvts[i]);
+
+	elvt_count = amd_read_elvt_count();
+	for (i = 0; i < elvt_count; i++)
+		lapic_early_mask_vec(&elvts[i]);
+}
+
 void
 lapic_setup(int boot)
 {