Whenever we load the GDT, we need to reload the segment selectors so their hidden data (base, limit, type, etc.) would be reloaded. It appears that loading GS overwrites the GS bases, so reload GS base after loading the segment to prevent per-cpu variable corruption. Signed-off-by: Nadav Amit <nadav.amit@xxxxxxxxx> --- x86/cstart64.S | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-) diff --git a/x86/cstart64.S b/x86/cstart64.S index c5561e7..9791282 100644 --- a/x86/cstart64.S +++ b/x86/cstart64.S @@ -118,6 +118,21 @@ MSR_GS_BASE = 0xc0000101 wrmsr .endm +.macro setup_segments + mov $MSR_GS_BASE, %ecx + rdmsr + + mov $0x10, %bx + mov %bx, %ds + mov %bx, %es + mov %bx, %fs + mov %bx, %gs + mov %bx, %ss + + /* restore MSR_GS_BASE */ + wrmsr +.endm + .globl start start: mov %ebx, mb_boot_info @@ -149,6 +164,7 @@ switch_to_5level: prepare_64: lgdt gdt64_desc + setup_segments enter_long_mode: mov %cr4, %eax @@ -196,12 +212,7 @@ sipi_end: .code32 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 -- 2.17.1
