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KVM: x86: Keep the lock order consistent between SRCU and gpc spinlock

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Acquire SRCU before taking the gpc spinlock in wait_pending_event() so as
to be consistent with all other functions that acquire both locks.  It's
not illegal to acquire SRCU inside a spinlock, nor is there deadlock
potential, but in general it's preferable to order locks from least
restrictive to most restrictive, e.g. if wait_pending_event() needed to
sleep for whatever reason, it could do so while holding SRCU, but would
need to drop the spinlock.

Signed-off-by: Peng Hao <flyingpeng@tencent.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/CAPm50a++Cb=QfnjMZ2EnCj-Sb9Y4UM-=uOEtHAcjnNLCAAf-dQ@mail.gmail.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Peng Hao
2022-11-08 11:50:54 +08:00
committed by Sean Christopherson
parent eb3992e833
commit 4265df667b
1 changed files with 2 additions and 2 deletions
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4
arch/x86/kvm/xen.c
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@@ -1165,8 +1165,8 @@ static bool wait_pending_event(struct kvm_vcpu *vcpu, int nr_ports,
bool ret = true;
int idx, i;
read_lock_irqsave(&gpc->lock, flags);
idx = srcu_read_lock(&kvm->srcu);
read_lock_irqsave(&gpc->lock, flags);
if (!kvm_gpc_check(kvm, gpc, gpc->gpa, PAGE_SIZE))
goto out_rcu;
@@ -1187,8 +1187,8 @@ static bool wait_pending_event(struct kvm_vcpu *vcpu, int nr_ports,
}
out_rcu:
srcu_read_unlock(&kvm->srcu, idx);
read_unlock_irqrestore(&gpc->lock, flags);
srcu_read_unlock(&kvm->srcu, idx);
return ret;
}