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authorChristoffer Dall <christoffer.dall@linaro.org>2017-12-04 21:35:23 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2017-12-14 09:26:49 +0100
commitec7660ccdd2b71d8c7f0243f8590253713e9b75d (patch)
treec745134c653e1f9a1d08decdd179f4fd742dd024 /virt
parent8eb73e2d410f00d383023fe41c0c25c6195b7389 (diff)
downloadlinux-ec7660ccdd2b71d8c7f0243f8590253713e9b75d.tar.bz2
KVM: Take vcpu->mutex outside vcpu_load
As we're about to call vcpu_load() from architecture-specific implementations of the KVM vcpu ioctls, but yet we access data structures protected by the vcpu->mutex in the generic code, factor this logic out from vcpu_load(). x86 is the only architecture which calls vcpu_load() outside of the main vcpu ioctl function, and these calls will no longer take the vcpu mutex following this patch. However, with the exception of kvm_arch_vcpu_postcreate (see below), the callers are either in the creation or destruction path of the VCPU, which means there cannot be any concurrent access to the data structure, because the file descriptor is not yet accessible, or is already gone. kvm_arch_vcpu_postcreate makes the newly created vcpu potentially accessible by other in-kernel threads through the kvm->vcpus array, and we therefore take the vcpu mutex in this case directly. Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org> Reviewed-by: Cornelia Huck <cohuck@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/kvm_main.c17
1 files changed, 6 insertions, 11 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index bc092e3d1d73..c4d116b336f4 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -151,17 +151,12 @@ bool kvm_is_reserved_pfn(kvm_pfn_t pfn)
/*
* Switches to specified vcpu, until a matching vcpu_put()
*/
-int vcpu_load(struct kvm_vcpu *vcpu)
+void vcpu_load(struct kvm_vcpu *vcpu)
{
- int cpu;
-
- if (mutex_lock_killable(&vcpu->mutex))
- return -EINTR;
- cpu = get_cpu();
+ int cpu = get_cpu();
preempt_notifier_register(&vcpu->preempt_notifier);
kvm_arch_vcpu_load(vcpu, cpu);
put_cpu();
- return 0;
}
EXPORT_SYMBOL_GPL(vcpu_load);
@@ -171,7 +166,6 @@ void vcpu_put(struct kvm_vcpu *vcpu)
kvm_arch_vcpu_put(vcpu);
preempt_notifier_unregister(&vcpu->preempt_notifier);
preempt_enable();
- mutex_unlock(&vcpu->mutex);
}
EXPORT_SYMBOL_GPL(vcpu_put);
@@ -2560,9 +2554,9 @@ static long kvm_vcpu_ioctl(struct file *filp,
#endif
- r = vcpu_load(vcpu);
- if (r)
- return r;
+ if (mutex_lock_killable(&vcpu->mutex))
+ return -EINTR;
+ vcpu_load(vcpu);
switch (ioctl) {
case KVM_RUN: {
struct pid *oldpid;
@@ -2735,6 +2729,7 @@ out_free1:
}
out:
vcpu_put(vcpu);
+ mutex_unlock(&vcpu->mutex);
kfree(fpu);
kfree(kvm_sregs);
return r;