Re: [PATCH 05/10] KVM: Adds ability to signal userspace using a file-descriptor

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Gregory Haskins wrote:
> Signed-off-by: Gregory Haskins <ghaskins-Et1tbQHTxzrQT0dZR+AlfA@public.gmane.org>
>   

Please include patch descriptions.

> ---
>
>  drivers/kvm/kvm.h      |    2 +
>  drivers/kvm/kvm_main.c |   82 ++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 84 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
> index 7b5d5e6..1c46830 100644
> --- a/drivers/kvm/kvm.h
> +++ b/drivers/kvm/kvm.h
> @@ -333,6 +333,8 @@ struct kvm_vcpu_irq {
>  	int                  deferred;
>  	struct task_struct  *task;
>  	int                  guest_mode;
> +	wait_queue_head_t    wq;
> +	int                  usignal;
>  };
>  
>  struct kvm_vcpu {
> diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
> index 3304cce..9a6d2c5 100644
> --- a/drivers/kvm/kvm_main.c
> +++ b/drivers/kvm/kvm_main.c
> @@ -40,6 +40,7 @@
>  #include <linux/file.h>
>  #include <linux/fs.h>
>  #include <linux/mount.h>
> +#include <linux/poll.h>
>  
>  #include "x86_emulate.h"
>  #include "segment_descriptor.h"
> @@ -326,6 +327,7 @@ static struct kvm *kvm_create_vm(void)
>  		memset(&vcpu->irq, 0, sizeof(vcpu->irq));
>  		spin_lock_init(&vcpu->irq.lock);
>  		vcpu->irq.deferred = -1;
> +		init_waitqueue_head(&vcpu->irq.wq);
>  
>  		vcpu->cpu = -1;
>  		vcpu->kvm = kvm;
> @@ -2288,11 +2290,78 @@ static int kvm_vcpu_release(struct inode *inode, struct file *filp)
>  	return 0;
>  }
>  
> +static unsigned int kvm_vcpu_poll(struct file *filp, poll_table *wait)
> +{
> +	struct kvm_vcpu *vcpu = filp->private_data;
> +	unsigned int events = 0;
> +	unsigned long flags;
> +
> +	poll_wait(filp, &vcpu->irq.wq, wait);
> +
> +	spin_lock_irqsave(&vcpu->irq.lock, flags);
> +	if (vcpu->irq.usignal)
> +		events |= POLLIN;
> +	spin_unlock_irqrestore(&vcpu->irq.lock, flags);
> +
> +	return events;
> +}
> +
> +static ssize_t kvm_vcpu_read(struct file *filp, char __user *buf, size_t count,
> +			     loff_t *ppos)
> +{
>   

Is having a read() (or a write()) actually necessary?

> +
> +	if (indirect_sig && waitqueue_active(&vcpu->irq.wq))
> +		wake_up(&vcpu->irq.wq);
>  }
>  
>   

Did you check that we can actually deliver signals with this?  I think a 
fasync_struct or something like that is necessary, but not sure.

Another implementation option (which I've only thought of now, sorry) is 
to have an ioctl which returns a real eventfd, reducing some code 
duplication.

-- 
error compiling committee.c: too many arguments to function


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