From 4461bbc05bf11fa4251acded60e4645863a4158a Mon Sep 17 00:00:00 2001 From: Boris Ostrovsky Date: Thu, 10 Apr 2014 12:17:09 -0400 Subject: [PATCH] x86/xen: Fix 32-bit PV guests's usage of kernel_stack Commit 198d208df4371734ac4728f69cb585c284d20a15 ("x86: Keep thread_info on thread stack in x86_32") made 32-bit kernels use kernel_stack to point to thread_info. That change missed a couple of updates needed by Xen's 32-bit PV guests: 1. kernel_stack needs to be initialized for secondary CPUs 2. GET_THREAD_INFO() now uses %fs register which may not be the kernel's version when executing xen_iret(). With respect to the second issue, we don't need GET_THREAD_INFO() anymore: we used it as an intermediate step to get to per_cpu xen_vcpu and avoid referencing %fs. Now that we are going to use %fs anyway we may as well go directly to xen_vcpu. Signed-off-by: Boris Ostrovsky Signed-off-by: David Vrabel --- arch/x86/xen/smp.c | 3 ++- arch/x86/xen/xen-asm_32.S | 25 +++++++++++++++++-------- 2 files changed, 19 insertions(+), 9 deletions(-) diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c index a18eadd8bb40..7005974c3ff3 100644 --- a/arch/x86/xen/smp.c +++ b/arch/x86/xen/smp.c @@ -441,10 +441,11 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct *idle) irq_ctx_init(cpu); #else clear_tsk_thread_flag(idle, TIF_FORK); +#endif per_cpu(kernel_stack, cpu) = (unsigned long)task_stack_page(idle) - KERNEL_STACK_OFFSET + THREAD_SIZE; -#endif + xen_setup_runstate_info(cpu); xen_setup_timer(cpu); xen_init_lock_cpu(cpu); diff --git a/arch/x86/xen/xen-asm_32.S b/arch/x86/xen/xen-asm_32.S index 33ca6e42a4ca..fd92a64d748e 100644 --- a/arch/x86/xen/xen-asm_32.S +++ b/arch/x86/xen/xen-asm_32.S @@ -75,6 +75,17 @@ ENDPROC(xen_sysexit) * stack state in whatever form its in, we keep things simple by only * using a single register which is pushed/popped on the stack. */ + +.macro POP_FS +1: + popw %fs +.pushsection .fixup, "ax" +2: movw $0, (%esp) + jmp 1b +.popsection + _ASM_EXTABLE(1b,2b) +.endm + ENTRY(xen_iret) /* test eflags for special cases */ testl $(X86_EFLAGS_VM | XEN_EFLAGS_NMI), 8(%esp) @@ -83,15 +94,13 @@ ENTRY(xen_iret) push %eax ESP_OFFSET=4 # bytes pushed onto stack - /* - * Store vcpu_info pointer for easy access. Do it this way to - * avoid having to reload %fs - */ + /* Store vcpu_info pointer for easy access */ #ifdef CONFIG_SMP - GET_THREAD_INFO(%eax) - movl %ss:TI_cpu(%eax), %eax - movl %ss:__per_cpu_offset(,%eax,4), %eax - mov %ss:xen_vcpu(%eax), %eax + pushw %fs + movl $(__KERNEL_PERCPU), %eax + movl %eax, %fs + movl %fs:xen_vcpu, %eax + POP_FS #else movl %ss:xen_vcpu, %eax #endif