Message-ID: <20090622130827.GD12867@redhat.com>
Date:	Mon, 22 Jun 2009 16:08:27 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Gregory Haskins <gregory.haskins@...il.com>
Cc:	Gregory Haskins <ghaskins@...ell.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, avi@...hat.com, mtosatti@...hat.com,
	paulmck@...ux.vnet.ibm.com, markmc@...hat.com
Subject: Re: [KVM PATCH v8 3/3] KVM: add iosignalfd support

On Mon, Jun 22, 2009 at 08:56:28AM -0400, Gregory Haskins wrote:
> Michael S. Tsirkin wrote:
> > On Mon, Jun 22, 2009 at 08:13:48AM -0400, Gregory Haskins wrote:
> >   
> >>>> + * notification when the memory has been touched.
> >>>> + * --------------------------------------------------------------------
> >>>> + */
> >>>> +
> >>>> +/*
> >>>> + * Design note: We create one PIO/MMIO device (iosignalfd_group) which
> >>>> + * aggregates  one or more iosignalfd_items.  Each item points to exactly one
> >>>>         
> >                    ^^                             ^^
> >   
> >>>> + * eventfd, and can be registered to trigger on any write to the group
> >>>> + * (wildcard), or to a write of a specific value.  If more than one item is to
> >>>>         
> >                                                        ^^
> >   
> >>>> + * be supported, the addr/len ranges must all be identical in the group.  If a
> >>>>         
> >                                                                               ^^
> >   
> >>>> + * trigger value is to be supported on a particular item, the group range must
> >>>> + * be exactly the width of the trigger.
> >>>>     
> >>>>         
> >>> Some duplicate spaces in the text above, apparently at random places.
> >>>
> >>>   
> >>>       
> >> -ENOPARSE ;)
> >>
> >> Can you elaborate?
> >>     
> >
> >
> > Marked with ^^
> >   
> Heh...well, the first one ("aggregates   one") is just a plain typo. 
> The others are just me showing my age, perhaps:
> 
> http://desktoppub.about.com/cs/typespacing/a/onetwospaces.htm
> 
> Whether right or wrong, I think I use two-spaces-after-a-period
> everywhere.

Ah, I see now. Naturally it is really up to you.

>  I can fix these if they bother you, but I suspect just
> about every comment I've written has them too. ;)
> 
> -Greg

It doesn't bother me as such. But you seem to care about such things :).
If you do care, other comments in kvm don't seem to be like this and
people won't remember to add spaces in comments, though.

> 
> >   
> >>>> + */
> >>>> +
> >>>> +struct _iosignalfd_item {
> >>>> +	struct list_head     list;
> >>>> +	struct file         *file;
> >>>> +	u64                  match;
> >>>> +	struct rcu_head      rcu;
> >>>> +	int                  wildcard:1;
> >>>> +};
> >>>> +
> >>>> +struct _iosignalfd_group {
> >>>> +	struct list_head     list;
> >>>> +	u64                  addr;
> >>>> +	size_t               length;
> >>>> +	size_t               count;
> >>>> +	struct list_head     items;
> >>>> +	struct kvm_io_device dev;
> >>>> +	struct rcu_head      rcu;
> >>>> +};
> >>>> +
> >>>> +static inline struct _iosignalfd_group *
> >>>> +to_group(struct kvm_io_device *dev)
> >>>> +{
> >>>> +	return container_of(dev, struct _iosignalfd_group, dev);
> >>>> +}
> >>>> +
> >>>> +static void
> >>>> +iosignalfd_item_free(struct _iosignalfd_item *item)
> >>>> +{
> >>>> +	fput(item->file);
> >>>> +	kfree(item);
> >>>> +}
> >>>> +
> >>>> +static void
> >>>> +iosignalfd_item_deferred_free(struct rcu_head *rhp)
> >>>> +{
> >>>> +	struct _iosignalfd_item *item;
> >>>> +
> >>>> +	item = container_of(rhp, struct _iosignalfd_item, rcu);
> >>>> +
> >>>> +	iosignalfd_item_free(item);
> >>>> +}
> >>>> +
> >>>> +static void
> >>>> +iosignalfd_group_deferred_free(struct rcu_head *rhp)
> >>>> +{
> >>>> +	struct _iosignalfd_group *group;
> >>>> +
> >>>> +	group = container_of(rhp, struct _iosignalfd_group, rcu);
> >>>> +
> >>>> +	kfree(group);
> >>>> +}
> >>>> +
> >>>> +static int
> >>>> +iosignalfd_group_in_range(struct kvm_io_device *this, gpa_t addr, int len,
> >>>> +			  int is_write)
> >>>> +{
> >>>> +	struct _iosignalfd_group *p = to_group(this);
> >>>> +
> >>>> +	return ((addr >= p->addr && (addr < p->addr + p->length)));
> >>>> +}
> >>>>     
> >>>>         
> >>> What does this test? len is ignored ...
> >>>
> >>>   
> >>>       
> >> Yeah, I was following precedent with other IO devices.  However, this
> >> *is* sloppy, I agree.  Will fix.
> >>
> >>     
> >>>> +
> >>>> +static int
> >>>>     
> >>>>         
> >>> This seems to be returning bool ...
> >>>   
> >>>       
> >> Ack
> >>     
> >>>   
> >>>       
> >>>> +iosignalfd_is_match(struct _iosignalfd_group *group,
> >>>> +		    struct _iosignalfd_item *item,
> >>>> +		    const void *val,
> >>>> +		    int len)
> >>>> +{
> >>>> +	u64 _val;
> >>>> +
> >>>> +	if (len != group->length)
> >>>> +		/* mis-matched length is always a miss */
> >>>> +		return false;
> >>>>     
> >>>>         
> >>> Why is that? what if there's 8 byte write which covers
> >>> a 4 byte group?
> >>>   
> >>>       
> >> v7 and earlier used to allow that for wildcards, actually.   It of
> >> course would never make sense to allow mis-matched writes for
> >> non-wildcards, since the idea is to match the value exactly.  However,
> >> the feedback I got from Avi was that we should make the wildcard vs
> >> non-wildcard access symmetrical and ensure they both conform to the size.
> >>     
> >>>   
> >>>       
> >>>> +
> >>>> +	if (item->wildcard)
> >>>> +		/* wildcard is always a hit */
> >>>> +		return true;
> >>>> +
> >>>> +	/* otherwise, we have to actually compare the data */
> >>>> +
> >>>> +	if (!IS_ALIGNED((unsigned long)val, len))
> >>>> +		/* protect against this request causing a SIGBUS */
> >>>> +		return false;
> >>>>     
> >>>>         
> >>> Could you explain what this does please?
> >>>   
> >>>       
> >> Sure:  item->match is a fixed u64 to represent all group->length
> >> values.  So it might have a 1, 2, 4, or 8 byte value in it.  When I
> >> write arrives, we need to cast the data-register (in this case
> >> represented by (void*)val) into a u64 so the equality check (see [A],
> >> below) can be done.  However, you can't cast an unaligned pointer, or it
> >> will SIGBUS on many (most?) architectures.
> >>     
> >
> > I mean guest access. Does it have to be aligned?
> > You could memcpy the value...
> >
> >   
> >>> I thought misaligned accesses are allowed.
> >>>   
> >>>       
> >> If thats true, we are in trouble ;)
> >>     
> >
> > I think it works at least on x86:
> > http://en.wikipedia.org/wiki/Packed#x86_and_x86-64
> >
> >   
> >>>   
> >>>       
> >>>> +
> >>>> +	switch (len) {
> >>>> +	case 1:
> >>>> +		_val = *(u8 *)val;
> >>>> +		break;
> >>>> +	case 2:
> >>>> +		_val = *(u16 *)val;
> >>>> +		break;
> >>>> +	case 4:
> >>>> +		_val = *(u32 *)val;
> >>>> +		break;
> >>>> +	case 8:
> >>>> +		_val = *(u64 *)val;
> >>>> +		break;
> >>>> +	default:
> >>>> +		return false;
> >>>> +	}
> >>>>     
> >>>>         
> >>> So legal values for len are 1,2,4 and 8?
> >>> Might be a good idea to document this.
> >>>
> >>>   
> >>>       
> >> Ack
> >>
> >>     
> >>>> +
> >>>> +	return _val == item->match;
> >>>>     
> >>>>         
> >> [A]
> >>
> >>     
> >>>> +}
> >>>> +
> >>>> +/*
> >>>> + * MMIO/PIO writes trigger an event (if the data matches).
> >>>> + *
> >>>> + * This is invoked by the io_bus subsystem in response to an address match
> >>>> + * against the group.  We must then walk the list of individual items to check
> >>>> + * for a match and, if applicable, to send the appropriate signal. If the item
> >>>> + * in question does not have a "match" pointer, it is considered a wildcard
> >>>> + * and will always generate a signal.  There can be an arbitrary number
> >>>> + * of distinct matches or wildcards per group.
> >>>> + */
> >>>> +static void
> >>>> +iosignalfd_group_write(struct kvm_io_device *this, gpa_t addr, int len,
> >>>> +		       const void *val)
> >>>> +{
> >>>> +	struct _iosignalfd_group *group = to_group(this);
> >>>> +	struct _iosignalfd_item *item;
> >>>> +
> >>>> +	rcu_read_lock();
> >>>> +
> >>>> +	list_for_each_entry_rcu(item, &group->items, list) {
> >>>> +		if (iosignalfd_is_match(group, item, val, len))
> >>>> +			eventfd_signal(item->file, 1);
> >>>> +	}
> >>>> +
> >>>> +	rcu_read_unlock();
> >>>> +}
> >>>> +
> >>>> +/*
> >>>> + * MMIO/PIO reads against the group indiscriminately return all zeros
> >>>> + */
> >>>>     
> >>>>         
> >>> Does it have to be so? It would be better to bounce reads to
> >>> userspace...
> >>>
> >>>   
> >>>       
> >> Good idea.  I can set is_write = false and I should never get this
> >> function called.
> >>
> >>     
> >>>> +static void
> >>>> +iosignalfd_group_read(struct kvm_io_device *this, gpa_t addr, int len,
> >>>> +		      void *val)
> >>>> +{
> >>>> +	memset(val, 0, len);
> >>>> +}
> >>>> +
> >>>> +/*
> >>>> + * This function is called as KVM is completely shutting down.  We do not
> >>>> + * need to worry about locking or careful RCU dancing...just nuke anything
> >>>> + * we have as quickly as possible
> >>>> + */
> >>>> +static void
> >>>> +iosignalfd_group_destructor(struct kvm_io_device *this)
> >>>> +{
> >>>> +	struct _iosignalfd_group *group = to_group(this);
> >>>> +	struct _iosignalfd_item *item, *tmp;
> >>>> +
> >>>> +	list_for_each_entry_safe(item, tmp, &group->items, list) {
> >>>> +		list_del(&item->list);
> >>>> +		iosignalfd_item_free(item);
> >>>> +	}
> >>>> +
> >>>> +	list_del(&group->list);
> >>>> +	kfree(group);
> >>>> +}
> >>>> +
> >>>> +static const struct kvm_io_device_ops iosignalfd_ops = {
> >>>> +	.read       = iosignalfd_group_read,
> >>>> +	.write      = iosignalfd_group_write,
> >>>> +	.in_range   = iosignalfd_group_in_range,
> >>>> +	.destructor = iosignalfd_group_destructor,
> >>>> +};
> >>>> +
> >>>> +/* assumes kvm->lock held */
> >>>> +static struct _iosignalfd_group *
> >>>> +iosignalfd_group_find(struct kvm *kvm, u64 addr)
> >>>> +{
> >>>> +	struct _iosignalfd_group *group;
> >>>> +
> >>>> +	list_for_each_entry(group, &kvm->iosignalfds, list) {
> >>>>     
> >>>>         
> >>> {} not needed here
> >>>   
> >>>       
> >> Ack
> >>     
> >>>   
> >>>       
> >>>> +		if (group->addr == addr)
> >>>> +			return group;
> >>>> +	}
> >>>> +
> >>>> +	return NULL;
> >>>> +}
> >>>> +
> >>>> +/* assumes kvm->lock is held */
> >>>> +static struct _iosignalfd_group *
> >>>> +iosignalfd_group_create(struct kvm *kvm, struct kvm_io_bus *bus,
> >>>> +			u64 addr, size_t len)
> >>>> +{
> >>>> +	struct _iosignalfd_group *group;
> >>>> +	int ret;
> >>>> +
> >>>> +	group = kzalloc(sizeof(*group), GFP_KERNEL);
> >>>> +	if (!group)
> >>>> +		return ERR_PTR(-ENOMEM);
> >>>> +
> >>>> +	INIT_LIST_HEAD(&group->list);
> >>>> +	INIT_LIST_HEAD(&group->items);
> >>>> +	group->addr   = addr;
> >>>> +	group->length = len;
> >>>> +	kvm_iodevice_init(&group->dev, &iosignalfd_ops);
> >>>> +
> >>>> +	ret = kvm_io_bus_register_dev(kvm, bus, &group->dev);
> >>>> +	if (ret < 0) {
> >>>> +		kfree(group);
> >>>> +		return ERR_PTR(ret);
> >>>> +	}
> >>>> +
> >>>> +	list_add_tail(&group->list, &kvm->iosignalfds);
> >>>> +
> >>>> +	return group;
> >>>> +}
> >>>> +
> >>>> +static int
> >>>> +kvm_assign_iosignalfd(struct kvm *kvm, struct kvm_iosignalfd *args)
> >>>> +{
> >>>> +	int                       pio = args->flags & KVM_IOSIGNALFD_FLAG_PIO;
> >>>> +	struct kvm_io_bus        *bus = pio ? &kvm->pio_bus : &kvm->mmio_bus;
> >>>> +	struct _iosignalfd_group *group = NULL;
> >>>>     
> >>>>         
> >>> why does group need to be initialized?
> >>>
> >>>   
> >>>       
> >>>> +	struct _iosignalfd_item  *item = NULL;
> >>>>     
> >>>>         
> >>> Why does item need to be initialized?
> >>>
> >>>   
> >>>       
> >> Probably leftover from versions prior to v8.  Will fix.
> >>
> >>     
> >>>> +	struct file              *file;
> >>>> +	int                       ret;
> >>>> +
> >>>> +	if (args->len > sizeof(u64))
> >>>>     
> >>>>         
> >>> Is e.g. value 3 legal?
> >>>   
> >>>       
> >> Ack.  Will check against legal values.
> >>
> >>     
> >>>   
> >>>       
> >>>> +		return -EINVAL;
> >>>>     
> >>>>         
> >>>   
> >>>       
> >>>> +
> >>>> +	file = eventfd_fget(args->fd);
> >>>> +	if (IS_ERR(file))
> >>>> +		return PTR_ERR(file);
> >>>> +
> >>>> +	item = kzalloc(sizeof(*item), GFP_KERNEL);
> >>>> +	if (!item) {
> >>>> +		ret = -ENOMEM;
> >>>> +		goto fail;
> >>>> +	}
> >>>> +
> >>>> +	INIT_LIST_HEAD(&item->list);
> >>>> +	item->file = file;
> >>>> +
> >>>> +	/*
> >>>> +	 * A trigger address is optional, otherwise this is a wildcard
> >>>> +	 */
> >>>> +	if (args->flags & KVM_IOSIGNALFD_FLAG_TRIGGER)
> >>>> +		item->match = args->trigger;
> >>>> +	else
> >>>> +		item->wildcard = true;
> >>>> +
> >>>> +	mutex_lock(&kvm->lock);
> >>>> +
> >>>> +	/*
> >>>> +	 * Put an upper limit on the number of items we support
> >>>> +	 */
> >>>>     
> >>>>         
> >>> Groups and items, actually, right?
> >>>
> >>>   
> >>>       
> >> Yeah, though technically that is implicit when you say "items", since
> >> each group always has at least one item.  I will try to make this
> >> clearer, though.
> >>
> >>     
> >>>> +	if (kvm->io_device_count >= CONFIG_KVM_MAX_IO_DEVICES) {
> >>>> +		ret = -ENOSPC;
> >>>> +		goto unlock_fail;
> >>>> +	}
> >>>> +
> >>>> +	group = iosignalfd_group_find(kvm, args->addr);
> >>>> +	if (!group) {
> >>>> +
> >>>> +		group = iosignalfd_group_create(kvm, bus,
> >>>> +						args->addr, args->len);
> >>>> +		if (IS_ERR(group)) {
> >>>> +			ret = PTR_ERR(group);
> >>>> +			goto unlock_fail;
> >>>> +		}
> >>>> +
> >>>> +		/*
> >>>> +		 * Note: We do not increment io_device_count for the first item,
> >>>> +		 * as this is represented by the group device that we just
> >>>> +		 * registered.  Make sure we handle this properly when we
> >>>> +		 * deassign the last item
> >>>> +		 */
> >>>> +	} else {
> >>>> +
> >>>> +		if (group->length != args->len) {
> >>>> +			/*
> >>>> +			 * Existing groups must have the same addr/len tuple
> >>>> +			 * or we reject the request
> >>>> +			 */
> >>>> +			ret = -EINVAL;
> >>>> +			goto unlock_fail;
> >>>>     
> >>>>         
> >>> Most errors seem to trigger EINVAL. Applications will be
> >>> easier to debug if different errors are returned on
> >>> different mistakes.
> >>>       
> >> Yeah, agreed.  Will try to differentiate some errors here.
> >>
> >>     
> >>>  E.g. here EBUSY might be good. And same
> >>> in other places.
> >>>
> >>>   
> >>>       
> >> Actually, I think EBUSY is supposed to be a transitory error, and would
> >> not be appropriate to use here.  That said, your point is taken: Find
> >> more appropriate and descriptive errors.
> >>
> >>     
> >>>> +		}
> >>>> +
> >>>> +		kvm->io_device_count++;
> >>>> +	}
> >>>> +
> >>>> +	/*
> >>>> +	 * Note: We are committed to succeed at this point since we have
> >>>> +	 * (potentially) published a new group-device.  Any failure handling
> >>>> +	 * added in the future after this point will need to be carefully
> >>>> +	 * considered.
> >>>> +	 */
> >>>> +
> >>>> +	list_add_tail_rcu(&item->list, &group->items);
> >>>> +	group->count++;
> >>>> +
> >>>> +	mutex_unlock(&kvm->lock);
> >>>> +
> >>>> +	return 0;
> >>>> +
> >>>> +unlock_fail:
> >>>> +	mutex_unlock(&kvm->lock);
> >>>> +fail:
> >>>> +	if (item)
> >>>> +		/*
> >>>> +		 * it would have never made it to the group->items list
> >>>> +		 * in the failure path, so we dont need to worry about removing
> >>>> +		 * it
> >>>> +		 */
> >>>> +		kfree(item);
> >>>> +
> >>>> +	fput(file);
> >>>> +
> >>>> +	return ret;
> >>>> +}
> >>>> +
> >>>> +
> >>>> +static int
> >>>> +kvm_deassign_iosignalfd(struct kvm *kvm, struct kvm_iosignalfd *args)
> >>>> +{
> >>>> +	int                       pio = args->flags & KVM_IOSIGNALFD_FLAG_PIO;
> >>>> +	struct kvm_io_bus        *bus = pio ? &kvm->pio_bus : &kvm->mmio_bus;
> >>>> +	struct _iosignalfd_group *group;
> >>>> +	struct _iosignalfd_item  *item, *tmp;
> >>>> +	struct file              *file;
> >>>> +	int                       ret = 0;
> >>>> +
> >>>> +	file = eventfd_fget(args->fd);
> >>>> +	if (IS_ERR(file))
> >>>> +		return PTR_ERR(file);
> >>>> +
> >>>> +	mutex_lock(&kvm->lock);
> >>>> +
> >>>> +	group = iosignalfd_group_find(kvm, args->addr);
> >>>> +	if (!group) {
> >>>> +		ret = -EINVAL;
> >>>> +		goto out;
> >>>> +	}
> >>>> +
> >>>> +	/*
> >>>> +	 * Exhaustively search our group->items list for any items that might
> >>>> +	 * match the specified fd, and (carefully) remove each one found.
> >>>> +	 */
> >>>> +	list_for_each_entry_safe(item, tmp, &group->items, list) {
> >>>> +
> >>>> +		if (item->file != file)
> >>>> +			continue;
> >>>> +
> >>>> +		list_del_rcu(&item->list);
> >>>> +		group->count--;
> >>>> +		if (group->count)
> >>>> +			/*
> >>>> +			 * We only decrement the global count if this is *not*
> >>>> +			 * the last item.  The last item will be accounted for
> >>>> +			 * by the io_bus_unregister
> >>>> +			 */
> >>>> +			kvm->io_device_count--;
> >>>> +
> >>>> +		/*
> >>>> +		 * The item may be still referenced inside our group->write()
> >>>> +		 * path's RCU read-side CS, so defer the actual free to the
> >>>> +		 * next grace
> >>>> +		 */
> >>>> +		call_rcu(&item->rcu, iosignalfd_item_deferred_free);
> >>>> +	}
> >>>> +
> >>>> +	/*
> >>>> +	 * Check if the group is now completely vacated as a result of
> >>>> +	 * removing the items.  If so, unregister/delete it
> >>>> +	 */
> >>>> +	if (!group->count) {
> >>>> +
> >>>> +		kvm_io_bus_unregister_dev(kvm, bus, &group->dev);
> >>>> +
> >>>> +		/*
> >>>> +		 * Like the item, the group may also still be referenced as
> >>>> +		 * per above.  However, the kvm->iosignalfds list is not
> >>>> +		 * RCU protected (its protected by kvm->lock instead) so
> >>>> +		 * we can just plain-vanilla remove it.  What needs to be
> >>>> +		 * done carefully is the actual freeing of the group pointer
> >>>> +		 * since we walk the group->items list within the RCU CS.
> >>>> +		 */
> >>>> +		list_del(&group->list);
> >>>> +		call_rcu(&group->rcu, iosignalfd_group_deferred_free);
> >>>>     
> >>>>         
> >>> This is a deferred call, is it not, with no guarantee on when it will
> >>> run? If correct I think synchronize_rcu might be better here:
> >>> - can the module go away while iosignalfd_group_deferred_free is
> >>>   running?
> >>>   
> >>>       
> >> Good catch.  Once I go this route it will be easy to use SRCU instead of
> >> RCU, too.  So I will fix this up.
> >>
> >>
> >>     
> >>> - can eventfd be signalled *after* ioctl exits? If yes
> >>>   this might confuse applications if they use the eventfd
> >>>   for something else.
> >>>   
> >>>       
> >> Not by iosignalfd.  Once this function completes, we synchronously
> >> guarantee that no more IO activity will generate an event on the
> >> affected eventfds.  Of course, this has no bearing on whether some other
> >> producer wont signal, but that is beyond the scope of iosignalfd.
> >>     
> >>>   
> >>>       
> >>>> +	}
> >>>> +
> >>>> +out:
> >>>> +	mutex_unlock(&kvm->lock);
> >>>> +
> >>>> +	fput(file);
> >>>> +
> >>>> +	return ret;
> >>>> +}
> >>>> +
> >>>> +int
> >>>> +kvm_iosignalfd(struct kvm *kvm, struct kvm_iosignalfd *args)
> >>>> +{
> >>>> +	if (args->flags & KVM_IOSIGNALFD_FLAG_DEASSIGN)
> >>>> +		return kvm_deassign_iosignalfd(kvm, args);
> >>>> +
> >>>> +	return kvm_assign_iosignalfd(kvm, args);
> >>>> +}
> >>>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> >>>> index 42cbea7..e6495d4 100644
> >>>> --- a/virt/kvm/kvm_main.c
> >>>> +++ b/virt/kvm/kvm_main.c
> >>>> @@ -971,7 +971,7 @@ static struct kvm *kvm_create_vm(void)
> >>>>  	atomic_inc(&kvm->mm->mm_count);
> >>>>  	spin_lock_init(&kvm->mmu_lock);
> >>>>  	kvm_io_bus_init(&kvm->pio_bus);
> >>>> -	kvm_irqfd_init(kvm);
> >>>> +	kvm_eventfd_init(kvm);
> >>>>  	mutex_init(&kvm->lock);
> >>>>  	mutex_init(&kvm->irq_lock);
> >>>>  	kvm_io_bus_init(&kvm->mmio_bus);
> >>>> @@ -2227,6 +2227,15 @@ static long kvm_vm_ioctl(struct file *filp,
> >>>>  		r = kvm_irqfd(kvm, data.fd, data.gsi, data.flags);
> >>>>  		break;
> >>>>  	}
> >>>> +	case KVM_IOSIGNALFD: {
> >>>> +		struct kvm_iosignalfd data;
> >>>> +
> >>>> +		r = -EFAULT;
> >>>> +		if (copy_from_user(&data, argp, sizeof data))
> >>>> +			goto out;
> >>>> +		r = kvm_iosignalfd(kvm, &data);
> >>>> +		break;
> >>>> +	}
> >>>>  #ifdef CONFIG_KVM_APIC_ARCHITECTURE
> >>>>  	case KVM_SET_BOOT_CPU_ID:
> >>>>  		r = 0;
> >>>>
> >>>> --
> >>>> To unsubscribe from this list: send the line "unsubscribe kvm" in
> >>>> the body of a message to majordomo@...r.kernel.org
> >>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >>>>     
> >>>>         
> >> Thanks Michael,
> >> -Greg
> >>
> >>
> >>     
> >
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe kvm" in
> > the body of a message to majordomo@...r.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >   
> 
> 


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