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KVM: PPC: Book3S HV: Drop locks around call to kvmppc_pin_guest_page

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At the moment we call kvmppc_pin_guest_page() in kvmppc_update_vpa()
with two spinlocks held: the vcore lock and the vcpu->vpa_update_lock.
This is not good, since kvmppc_pin_guest_page() calls down_read() and
get_user_pages_fast(), both of which can sleep.  This bug was introduced
in 2e25aa5f ("KVM: PPC: Book3S HV: Make virtual processor area
registration more robust").

This arranges to drop those spinlocks before calling
kvmppc_pin_guest_page() and re-take them afterwards.  Dropping the
vcore lock in kvmppc_run_core() means we have to set the vcore_state
field to VCORE_RUNNING before we drop the lock, so that other vcpus
won't try to run this vcore.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Acked-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Paul Mackerras 2012-06-01 20:20:24 +10:00 committed by Avi Kivity
parent f961f72836
commit 081f323bd3
1 changed files with 66 additions and 30 deletions
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82
arch/powerpc/kvm/book3s_hv.c
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@ -268,16 +268,38 @@ static unsigned long do_h_register_vpa(struct kvm_vcpu *vcpu,
return err;
}
static void kvmppc_update_vpa(struct kvm *kvm, struct kvmppc_vpa *vpap)
static void kvmppc_update_vpa(struct kvm_vcpu *vcpu, struct kvmppc_vpa *vpap)
{
struct kvm *kvm = vcpu->kvm;
void *va;
unsigned long nb;
unsigned long gpa;
/*
* We need to pin the page pointed to by vpap->next_gpa,
* but we can't call kvmppc_pin_guest_page under the lock
* as it does get_user_pages() and down_read(). So we
* have to drop the lock, pin the page, then get the lock
* again and check that a new area didn't get registered
* in the meantime.
*/
for (;;) {
gpa = vpap->next_gpa;
spin_unlock(&vcpu->arch.vpa_update_lock);
va = NULL;
nb = 0;
if (gpa)
va = kvmppc_pin_guest_page(kvm, vpap->next_gpa, &nb);
spin_lock(&vcpu->arch.vpa_update_lock);
if (gpa == vpap->next_gpa)
break;
/* sigh... unpin that one and try again */
if (va)
kvmppc_unpin_guest_page(kvm, va);
}
vpap->update_pending = 0;
va = NULL;
if (vpap->next_gpa) {
va = kvmppc_pin_guest_page(kvm, vpap->next_gpa, &nb);
if (nb < vpap->len) {
if (va && nb < vpap->len) {
/*
* If it's now too short, it must be that userspace
* has changed the mappings underlying guest memory,
@ -286,7 +308,6 @@ static void kvmppc_update_vpa(struct kvm *kvm, struct kvmppc_vpa *vpap)
kvmppc_unpin_guest_page(kvm, va);
va = NULL;
}
}
if (vpap->pinned_addr)
kvmppc_unpin_guest_page(kvm, vpap->pinned_addr);
vpap->pinned_addr = va;
@ -296,20 +317,18 @@ static void kvmppc_update_vpa(struct kvm *kvm, struct kvmppc_vpa *vpap)
static void kvmppc_update_vpas(struct kvm_vcpu *vcpu)
{
struct kvm *kvm = vcpu->kvm;
spin_lock(&vcpu->arch.vpa_update_lock);
if (vcpu->arch.vpa.update_pending) {
kvmppc_update_vpa(kvm, &vcpu->arch.vpa);
kvmppc_update_vpa(vcpu, &vcpu->arch.vpa);
init_vpa(vcpu, vcpu->arch.vpa.pinned_addr);
}
if (vcpu->arch.dtl.update_pending) {
kvmppc_update_vpa(kvm, &vcpu->arch.dtl);
kvmppc_update_vpa(vcpu, &vcpu->arch.dtl);
vcpu->arch.dtl_ptr = vcpu->arch.dtl.pinned_addr;
vcpu->arch.dtl_index = 0;
}
if (vcpu->arch.slb_shadow.update_pending)
kvmppc_update_vpa(kvm, &vcpu->arch.slb_shadow);
kvmppc_update_vpa(vcpu, &vcpu->arch.slb_shadow);
spin_unlock(&vcpu->arch.vpa_update_lock);
}
@ -800,12 +819,39 @@ static int kvmppc_run_core(struct kvmppc_vcore *vc)
struct kvm_vcpu *vcpu, *vcpu0, *vnext;
long ret;
u64 now;
int ptid, i;
int ptid, i, need_vpa_update;
/* don't start if any threads have a signal pending */
list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list)
need_vpa_update = 0;
list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list) {
if (signal_pending(vcpu->arch.run_task))
return 0;
need_vpa_update |= vcpu->arch.vpa.update_pending |
vcpu->arch.slb_shadow.update_pending |
vcpu->arch.dtl.update_pending;
}
/*
* Initialize *vc, in particular vc->vcore_state, so we can
* drop the vcore lock if necessary.
*/
vc->n_woken = 0;
vc->nap_count = 0;
vc->entry_exit_count = 0;
vc->vcore_state = VCORE_RUNNING;
vc->in_guest = 0;
vc->napping_threads = 0;
/*
* Updating any of the vpas requires calling kvmppc_pin_guest_page,
* which can't be called with any spinlocks held.
*/
if (need_vpa_update) {
spin_unlock(&vc->lock);
list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list)
kvmppc_update_vpas(vcpu);
spin_lock(&vc->lock);
}
/*
* Make sure we are running on thread 0, and that
@ -838,20 +884,10 @@ static int kvmppc_run_core(struct kvmppc_vcore *vc)
if (vcpu->arch.ceded)
vcpu->arch.ptid = ptid++;
vc->n_woken = 0;
vc->nap_count = 0;
vc->entry_exit_count = 0;
vc->vcore_state = VCORE_RUNNING;
vc->stolen_tb += mftb() - vc->preempt_tb;
vc->in_guest = 0;
vc->pcpu = smp_processor_id();
vc->napping_threads = 0;
list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list) {
kvmppc_start_thread(vcpu);
if (vcpu->arch.vpa.update_pending ||
vcpu->arch.slb_shadow.update_pending ||
vcpu->arch.dtl.update_pending)
kvmppc_update_vpas(vcpu);
kvmppc_create_dtl_entry(vcpu, vc);
}
/* Grab any remaining hw threads so they can't go into the kernel */