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KVM: provide irq_unsafe kvm_guest_{enter|exit}

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Several kvm architectures disable interrupts before kvm_guest_enter.
kvm_guest_enter then uses local_irq_save/restore to disable interrupts
again or for the first time. Lets provide underscore versions of
kvm_guest_{enter|exit} that assume being called locked.
kvm_guest_enter now disables interrupts for the full function and
thus we can remove the check for preemptible.

This patch then adopts s390/kvm to use local_irq_disable/enable calls
which are slighty cheaper that local_irq_save/restore and call these
new functions.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Christian Borntraeger 2015-04-30 13:43:30 +02:00 committed by Paolo Bonzini
parent ff7bbb9c6a
commit 0097d12e50
2 changed files with 24 additions and 13 deletions
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10
arch/s390/kvm/kvm-s390.c
View File

@ -1993,12 +1993,14 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
* As PF_VCPU will be used in fault handler, between
* guest_enter and guest_exit should be no uaccess.
*/
preempt_disable();
kvm_guest_enter();
preempt_enable();
local_irq_disable();
__kvm_guest_enter();
local_irq_enable();
exit_reason = sie64a(vcpu->arch.sie_block,
vcpu->run->s.regs.gprs);
kvm_guest_exit();
local_irq_disable();
__kvm_guest_exit();
local_irq_enable();
vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
rc = vcpu_post_run(vcpu, exit_reason);

27
include/linux/kvm_host.h
View File

@ -762,16 +762,10 @@ static inline void kvm_iommu_unmap_pages(struct kvm *kvm,
}
#endif
static inline void kvm_guest_enter(void)
/* must be called with irqs disabled */
static inline void __kvm_guest_enter(void)
{
unsigned long flags;
BUG_ON(preemptible());
local_irq_save(flags);
guest_enter();
local_irq_restore(flags);
/* KVM does not hold any references to rcu protected data when it
* switches CPU into a guest mode. In fact switching to a guest mode
* is very similar to exiting to userspace from rcu point of view. In
@ -783,12 +777,27 @@ static inline void kvm_guest_enter(void)
rcu_virt_note_context_switch(smp_processor_id());
}
/* must be called with irqs disabled */
static inline void __kvm_guest_exit(void)
{
guest_exit();
}
static inline void kvm_guest_enter(void)
{
unsigned long flags;
local_irq_save(flags);
__kvm_guest_enter();
local_irq_restore(flags);
}
static inline void kvm_guest_exit(void)
{
unsigned long flags;
local_irq_save(flags);
guest_exit();
__kvm_guest_exit();
local_irq_restore(flags);
}