linux-kernel - Re: [KVM PATCH v8 3/3] KVM: add iosignalfd support

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Date:	Tue, 23 Jun 2009 07:40:32 -0400
From:	Gregory Haskins <ghaskins@...ell.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	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

Michael S. Tsirkin wrote:
> On Tue, Jun 23, 2009 at 07:33:07AM -0400, Gregory Haskins wrote:
>   
>> Michael S. Tsirkin wrote:
>>     
>>> On Thu, Jun 18, 2009 at 08:30:46PM -0400, Gregory Haskins wrote:
>>>   
>>>       
>>>> +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)));
>>>> +}
>>>>     
>>>>         
>>> I think I see a problem here. For virtio, we do not necessarily want all
>>> virtqueues for a device to live in kernel: there might be control
>>> virtqueues that we want to leave in userspace. Since this claims all
>>> writes to a specific address, the signal never makes it to userspace.
>>>
>>>   
>>>       
>> You can use a wildcard.  Would that work?
>>
>>     
>
> Nope, you need to know the value written.
>
>   
Note: You can also terminate an eventfd in userspace...it doesn't have
to terminate in-kernel.  Not sure if that helps.


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