x86/xen: Fix 32-bit PV guests's usage of kernel_stack

Commit 198d208df4 ("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 <boris.ostrovsky@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
This commit is contained in:
Boris Ostrovsky 2014-04-10 12:17:09 -04:00 committed by David Vrabel
parent d06eb3ee9b
commit 4461bbc05b
2 changed files with 19 additions and 9 deletions

View File

@ -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);

View File

@ -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