Commit 0097d12e authored by Christian Borntraeger's avatar Christian Borntraeger Committed by Paolo Bonzini
Browse files

KVM: provide irq_unsafe kvm_guest_{enter|exit} 



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: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent ff7bbb9c

arch/s390/kvm/kvm-s390.c

+6 −4
Original line number Diff line number Diff line
@@ -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);

include/linux/kvm_host.h

+18 −9
Original line number Diff line number Diff line
@@ -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);

}

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