xen: disable interrupts before saving in percpu
Impact: Fix race condition xen_mc_batch has a small preempt race where it takes the address of a percpu variable immediately before disabling interrupts, thereby leaving a small window in which we may migrate to another cpu and save the flags in the wrong percpu variable. Disable interrupts before saving the old flags in a percpu. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
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@ -19,8 +19,10 @@ DECLARE_PER_CPU(unsigned long, xen_mc_irq_flags);
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paired with xen_mc_issue() */
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paired with xen_mc_issue() */
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static inline void xen_mc_batch(void)
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static inline void xen_mc_batch(void)
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{
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{
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unsigned long flags;
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/* need to disable interrupts until this entry is complete */
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/* need to disable interrupts until this entry is complete */
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local_irq_save(__get_cpu_var(xen_mc_irq_flags));
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local_irq_save(flags);
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__get_cpu_var(xen_mc_irq_flags) = flags;
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}
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}
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static inline struct multicall_space xen_mc_entry(size_t args)
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static inline struct multicall_space xen_mc_entry(size_t args)
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