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KVM: mark requests that need synchronization

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kvm_make_all_requests() provides a synchronization that waits until all
kicked VCPUs have acknowledged the kick.  This is important for
KVM_REQ_MMU_RELOAD as it prevents freeing while lockless paging is
underway.

This patch adds the synchronization property into all requests that are
currently being used with kvm_make_all_requests() in order to preserve
the current behavior and only introduce a new framework.  Removing it
from requests where it is not necessary is left for future patches.

Signed-off-by: Radim Krčmář <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
This commit is contained in:
Paolo Bonzini 2017-04-27 14:33:43 +02:00
commit 7a97cec26b
5 changed files with 32 additions and 12 deletions
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25
virt/kvm/kvm_main.c
View file

@ -165,6 +165,24 @@ void vcpu_put(struct kvm_vcpu *vcpu)
}
EXPORT_SYMBOL_GPL(vcpu_put);
/* TODO: merge with kvm_arch_vcpu_should_kick */
static bool kvm_request_needs_ipi(struct kvm_vcpu *vcpu, unsigned req)
{
int mode = kvm_vcpu_exiting_guest_mode(vcpu);
/*
* We need to wait for the VCPU to reenable interrupts and get out of
* READING_SHADOW_PAGE_TABLES mode.
*/
if (req & KVM_REQUEST_WAIT)
return mode != OUTSIDE_GUEST_MODE;
/*
* Need to kick a running VCPU, but otherwise there is nothing to do.
*/
return mode == IN_GUEST_MODE;
}
static void ack_flush(void *_completed)
{
}
@ -174,6 +192,7 @@ bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
int i, cpu, me;
cpumask_var_t cpus;
bool called = true;
bool wait = req & KVM_REQUEST_WAIT;
struct kvm_vcpu *vcpu;
zalloc_cpumask_var(&cpus, GFP_ATOMIC);
@ -187,13 +206,13 @@ bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req)
continue;
if (cpus != NULL && cpu != -1 && cpu != me &&
kvm_vcpu_exiting_guest_mode(vcpu) != OUTSIDE_GUEST_MODE)
kvm_request_needs_ipi(vcpu, req))
cpumask_set_cpu(cpu, cpus);
}
if (unlikely(cpus == NULL))
smp_call_function_many(cpu_online_mask, ack_flush, NULL, 1);
smp_call_function_many(cpu_online_mask, ack_flush, NULL, wait);
else if (!cpumask_empty(cpus))
smp_call_function_many(cpus, ack_flush, NULL, 1);
smp_call_function_many(cpus, ack_flush, NULL, wait);
else
called = false;
put_cpu();