From 4461bbc05bf11fa4251acded60e4645863a4158a Mon Sep 17 00:00:00 2001 From: Boris Ostrovsky Date: Thu, 10 Apr 2014 12:17:09 -0400 Subject: 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(-) (limited to 'arch/x86') diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c index a18eadd..7005974 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 33ca6e4..fd92a64 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 -- cgit v1.1 From e0fc17a936334c08b2729fff87168c03fdecf5b6 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Fri, 4 Apr 2014 14:48:04 -0400 Subject: xen/spinlock: Don't enable them unconditionally. The git commit a945928ea2709bc0e8e8165d33aed855a0110279 ('xen: Do not enable spinlocks before jump_label_init() has executed') was added to deal with the jump machinery. Earlier the code that turned on the jump label was only called by Xen specific functions. But now that it had been moved to the initcall machinery it gets called on Xen, KVM, and baremetal - ouch!. And the detection machinery to only call it on Xen wasn't remembered in the heat of merge window excitement. This means that the slowpath is enabled on baremetal while it should not be. Reported-by: Waiman Long Acked-by: Steven Rostedt CC: stable@vger.kernel.org CC: Boris Ostrovsky Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: David Vrabel --- arch/x86/xen/spinlock.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'arch/x86') diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c index 4d3acc3..0ba5f3b 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -274,7 +274,7 @@ void __init xen_init_spinlocks(void) printk(KERN_DEBUG "xen: PV spinlocks disabled\n"); return; } - + printk(KERN_DEBUG "xen: PV spinlocks enabled\n"); pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(xen_lock_spinning); pv_lock_ops.unlock_kick = xen_unlock_kick; } @@ -290,6 +290,9 @@ static __init int xen_init_spinlocks_jump(void) if (!xen_pvspin) return 0; + if (!xen_domain()) + return 0; + static_key_slow_inc(¶virt_ticketlocks_enabled); return 0; } -- cgit v1.1