From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Thu, 11 Jul 2019 06:57:02 +0000 (-0700)
Subject: kernel - Zen 2 - Make sure %fs's selector is loaded in AP bootstrap
X-Git-Tag: v5.8.0rc1~1282
X-Git-Url: https://gitweb.dragonflybsd.org/dragonfly.git/commitdiff_plain/1a923442efb8ded428689c89162631d739cf0548

kernel - Zen 2 - Make sure %fs's selector is loaded in AP bootstrap

* Issue load_fs() in the AP bootstrap.  It appears that Zen 2 handles
  %fs in a weird way when the selector isn't loaded, causing the first
  wrmsr(MSR_FSBASE) to quietly fail, and possibly others too.

* For good measure, also issue load_ds() and load_es().

* Fixes DragonFlyBSD's boot on Zen 2.
---

diff --git a/sys/platform/pc64/x86_64/mp_machdep.c b/sys/platform/pc64/x86_64/mp_machdep.c
index 4a312d3b4d..af7d4eb4a4 100644
--- a/sys/platform/pc64/x86_64/mp_machdep.c
+++ b/sys/platform/pc64/x86_64/mp_machdep.c
@@ -136,6 +136,7 @@ int	current_postcode;
 /** XXX FIXME: what system files declare these??? */
 
 extern int naps;
+extern int _udatasel;
 
 int64_t tsc0_offset;
 extern int64_t tsc_offsets[];
@@ -269,6 +270,10 @@ init_secondary(void)
 
 	lidt(&r_idt_arr[mdcpu->mi.gd_cpuid]);
 
+	load_ds(_udatasel);
+	load_es(_udatasel);
+	load_fs(_udatasel);
+
 #if 0
 	lldt(_default_ldt);
 	mdcpu->gd_currentldt = _default_ldt;