From 8b2ac021f0dc6e02c5b4ca2aff013564c6824f40 Mon Sep 17 00:00:00 2001
From: br <br@FreeBSD.org>
Date: Wed, 13 Jun 2018 10:32:21 +0000
Subject: [PATCH] Don't jump to VA space until kernel is ready.

This fixes the race when first core sets up the pagetables, while
secondary cores do translating the address of __riscv_boot_ap.

This now allows us to smpboot in QEMU with 8 cores just fine.

Sponsored by:	DARPA, AFRL
---
 sys/riscv/riscv/locore.S | 29 +++++++++++++++--------------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/sys/riscv/riscv/locore.S b/sys/riscv/riscv/locore.S
index fb39402267e3..4b2e6ad6eed0 100644
--- a/sys/riscv/riscv/locore.S
+++ b/sys/riscv/riscv/locore.S
@@ -263,6 +263,21 @@ END(mpentry)
  * Called by a core when it is being brought online.
  */
 ENTRY(mpentry)
+	/*
+	 * Calculate the offset to __riscv_boot_ap
+	 * for the current core, cpuid is in a0.
+	 */
+	li	t1, 4
+	mulw	t1, t1, a0
+	/* Get the pointer */
+	la	t0, __riscv_boot_ap
+	add	t0, t0, t1
+
+1:
+	/* Wait the kernel to be ready */
+	lw	t1, 0(t0)
+	beqz	t1, 1b
+
 	/* Setup stack pointer */
 	la	t0, secondary_stacks
 	li	t1, (PAGE_SIZE * KSTACK_PAGES)
@@ -296,20 +311,6 @@ mpva:
 	/* Ensure sscratch is zero */
 	li	t0, 0
 	csrw	sscratch, t0
-	/*
-	 * Calculate the offset to __riscv_boot_ap
-	 * for current core, cpuid in a0.
-	 */
-	li	t1, 4
-	mulw	t1, t1, a0
-	/* Get pointer */
-	la	t0, __riscv_boot_ap
-	add	t0, t0, t1
-
-1:
-	/* Wait the kernel to be ready */
-	lw	t1, 0(t0)
-	beqz	t1, 1b
 
 	call	init_secondary
 END(mpentry)