x86: Initialize segment selectors
Currently, the BSP's segment selectors are not initialized in 32-bit
(cstart.S). As a result the tests implicitly rely on the segment
selector values that are set by the BIOS. If this assumption is not
kept, the task-switch test fails.
Fix it by initializing them.
Signed-off-by: Nadav Amit <namit@vmware.com>
Message-Id: <20200623084132.36213-1-namit@vmware.com>
Reviewed-by: Jim Mattson <jmattson@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/x86/cstart.S b/x86/cstart.S
index fa62e09..5ad70b5 100644
--- a/x86/cstart.S
+++ b/x86/cstart.S
@@ -94,6 +94,15 @@
wrmsr
.endm
+.macro setup_segments
+ mov $0x10, %ax
+ mov %ax, %ds
+ mov %ax, %es
+ mov %ax, %fs
+ mov %ax, %gs
+ mov %ax, %ss
+.endm
+
.globl start
start:
mov $stacktop, %esp
@@ -109,6 +118,7 @@
prepare_32:
lgdtl gdt32_descr
+ setup_segments
mov %cr4, %eax
bts $4, %eax // pse
@@ -133,12 +143,7 @@
retl
ap_start32:
- mov $0x10, %ax
- mov %ax, %ds
- mov %ax, %es
- mov %ax, %fs
- mov %ax, %gs
- mov %ax, %ss
+ setup_segments
mov $-4096, %esp
lock/xaddl %esp, smp_stacktop
setup_percpu_area
