From bc90aefa99f74452d549d503a3f1cbf3adc9c6bb Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Tue, 19 Dec 2023 16:12:00 +0100 Subject: [PATCH] x86/asm: Add DB flag to 32-bit percpu GDT entry The D/B size flag for the 32-bit percpu GDT entry was not set. The Intel manual (vol 3, section 3.4.5) only specifies the meaning of this flag for three cases: 1) code segments used for %cs -- doesn't apply here 2) stack segments used for %ss -- doesn't apply 3) expand-down data segments -- but we don't have the expand-down flag set, so it also doesn't apply here The flag likely doesn't do anything here, although the manual does also say: "This flag should always be set to 1 for 32-bit code and data segments [...]" so we should probably do it anyway. Signed-off-by: Vegard Nossum Signed-off-by: Ingo Molnar Acked-by: Linus Torvalds Link: https://lore.kernel.org/r/20231219151200.2878271-6-vegard.nossum@oracle.com --- arch/x86/kernel/setup_percpu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c index f2583de97a64..b30d6e180df7 100644 --- a/arch/x86/kernel/setup_percpu.c +++ b/arch/x86/kernel/setup_percpu.c @@ -106,7 +106,7 @@ void __init pcpu_populate_pte(unsigned long addr) static inline void setup_percpu_segment(int cpu) { #ifdef CONFIG_X86_32 - struct desc_struct d = GDT_ENTRY_INIT(DESC_DATA32 & ~_DESC_DB, + struct desc_struct d = GDT_ENTRY_INIT(DESC_DATA32, per_cpu_offset(cpu), 0xFFFFF); write_gdt_entry(get_cpu_gdt_rw(cpu), GDT_ENTRY_PERCPU, &d, DESCTYPE_S);