From 99a10da1b4fee8ef7a096e5fd3608f6c15932eb0 Mon Sep 17 00:00:00 2001 From: Andrew Cooper Date: Mon, 28 Nov 2016 09:17:00 +0100 Subject: [PATCH] x86/cpu: reposition stack alignment check As identified during review, using BUG_ON() before `lidt` will result in a triple fault, even on APs. Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich Release-acked-by: Wei Liu --- xen/arch/x86/cpu/common.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c index 06ee401ff1..1d78ab4d84 100644 --- a/xen/arch/x86/cpu/common.c +++ b/xen/arch/x86/cpu/common.c @@ -643,11 +643,6 @@ void load_system_tables(void) .limit = (IDT_ENTRIES * sizeof(idt_entry_t)) - 1, }; - /* Bottom-of-stack must be 16-byte aligned! */ - BUILD_BUG_ON((sizeof(struct cpu_info) - - offsetof(struct cpu_info, guest_cpu_user_regs.es)) & 0xf); - BUG_ON(system_state != SYS_STATE_early_boot && (stack_bottom & 0xf)); - /* Main stack for interrupts/exceptions. */ tss->rsp0 = stack_bottom; tss->bitmap = IOBMP_INVALID_OFFSET; @@ -672,6 +667,15 @@ void load_system_tables(void) asm volatile ("lidt %0" : : "m" (idtr) ); asm volatile ("ltr %w0" : : "rm" (TSS_ENTRY << 3) ); asm volatile ("lldt %w0" : : "rm" (0) ); + + /* + * Bottom-of-stack must be 16-byte aligned! + * + * Defer checks until exception support is sufficiently set up. + */ + BUILD_BUG_ON((sizeof(struct cpu_info) - + offsetof(struct cpu_info, guest_cpu_user_regs.es)) & 0xf); + BUG_ON(system_state != SYS_STATE_early_boot && (stack_bottom & 0xf)); } /* -- 2.30.2