From a945928ea2709bc0e8e8165d33aed855a0110279 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Thu, 12 Sep 2013 22:29:44 -0400 Subject: xen: Do not enable spinlocks before jump_label_init() has executed xen_init_spinlocks() currently calls static_key_slow_inc() before jump_label_init() is invoked. When CONFIG_JUMP_LABEL is set (which usually is the case) the effect of this static_key_slow_inc() is deferred until after jump_label_init(). This is different from when CONFIG_JUMP_LABEL is not set, in which case the key is set immediately. Thus, depending on the value of config option, we may observe different behavior. In addition, when we come to __jump_label_transform() from jump_label_init(), the key (paravirt_ticketlocks_enabled) is already enabled. On processors where ideal_nop is not the same as default_nop this will cause a BUG() since it is expected that before a key is enabled the latter is replaced by the former during initialization. To address this problem we need to move static_key_slow_inc(¶virt_ticketlocks_enabled) so that it is called after jump_label_init(). We also need to make sure that this is done before other cpus start to boot. early_initcall appears to be a good place to do so. (Note that we cannot move whole xen_init_spinlocks() there since pv_lock_ops need to be set before alternative_instructions() runs.) Signed-off-by: Konrad Rzeszutek Wilk [v2: Added extra comments in the code] Signed-off-by: Boris Ostrovsky Signed-off-by: Konrad Rzeszutek Wilk Reviewed-by: Steven Rostedt --- arch/x86/xen/spinlock.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) (limited to 'arch') diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c index 253f63fceea..be6b8607895 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -259,6 +259,14 @@ void xen_uninit_lock_cpu(int cpu) } +/* + * Our init of PV spinlocks is split in two init functions due to us + * using paravirt patching and jump labels patching and having to do + * all of this before SMP code is invoked. + * + * The paravirt patching needs to be done _before_ the alternative asm code + * is started, otherwise we would not patch the core kernel code. + */ void __init xen_init_spinlocks(void) { @@ -267,12 +275,26 @@ void __init xen_init_spinlocks(void) return; } - static_key_slow_inc(¶virt_ticketlocks_enabled); - pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(xen_lock_spinning); pv_lock_ops.unlock_kick = xen_unlock_kick; } +/* + * While the jump_label init code needs to happend _after_ the jump labels are + * enabled and before SMP is started. Hence we use pre-SMP initcall level + * init. We cannot do it in xen_init_spinlocks as that is done before + * jump labels are activated. + */ +static __init int xen_init_spinlocks_jump(void) +{ + if (!xen_pvspin) + return 0; + + static_key_slow_inc(¶virt_ticketlocks_enabled); + return 0; +} +early_initcall(xen_init_spinlocks_jump); + static __init int xen_parse_nopvspin(char *arg) { xen_pvspin = false; -- cgit v1.2.3-70-g09d2