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The first time a device is opened > > associate the group KVM with the device. > > > > Suggested-by: Jason Gunthorpe > > Signed-off-by: Matthew Rosato > > ... > > > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c > > index cfcff7764403..c5d421eda275 100644 > > +++ b/drivers/vfio/vfio.c > > @@ -10,6 +10,7 @@ > > * Author: Tom Lyon, pugs@cisco.com > > */ > > +#include "linux/kvm_host.h" > > #include > > #include > > #include > > @@ -1083,6 +1084,13 @@ static struct file *vfio_device_open(struct vfio_device *device) > > mutex_lock(&device->dev_set->lock); > > device->open_count++; > > + down_write(&device->group->group_rwsem); > > + if (device->open_count == 1 && device->group->kvm) { > > + device->kvm = device->group->kvm; > > + kvm_get_kvm(device->kvm); > > Did some more compile testing, since vfio has no hard kvm dependency, > kvm_get_kvm and kvm_put_kvm are an issue if KVM is a module while vfio is > built-in... Ugh, my other plan was to have the driver itself capture the kvm, ie we lock the group_rwsem to keep the group->kvm valid and then pass the kvm to open_device in some way, then the driver can kvm_get_kvm() it Alternatively, I don't know why kvm_get_kvm() is an exported symbol when it is just calling refcount_inc() - inlining it would be an improvement I think. 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The first time a device is opened > > associate the group KVM with the device. > > > > Suggested-by: Jason Gunthorpe > > Signed-off-by: Matthew Rosato > > ... > > > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c > > index cfcff7764403..c5d421eda275 100644 > > +++ b/drivers/vfio/vfio.c > > @@ -10,6 +10,7 @@ > > * Author: Tom Lyon, pugs@cisco.com > > */ > > +#include "linux/kvm_host.h" > > #include > > #include > > #include > > @@ -1083,6 +1084,13 @@ static struct file *vfio_device_open(struct vfio_device *device) > > mutex_lock(&device->dev_set->lock); > > device->open_count++; > > + down_write(&device->group->group_rwsem); > > + if (device->open_count == 1 && device->group->kvm) { > > + device->kvm = device->group->kvm; > > + kvm_get_kvm(device->kvm); > > Did some more compile testing, since vfio has no hard kvm dependency, > kvm_get_kvm and kvm_put_kvm are an issue if KVM is a module while vfio is > built-in... Ugh, my other plan was to have the driver itself capture the kvm, ie we lock the group_rwsem to keep the group->kvm valid and then pass the kvm to open_device in some way, then the driver can kvm_get_kvm() it Alternatively, I don't know why kvm_get_kvm() is an exported symbol when it is just calling refcount_inc() - inlining it would be an improvement I think. Jason