lkml.org 
[lkml]   [2009]   [Aug]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 0/2] eventfd: new EFD_STATE flag
On Wed, 26 Aug 2009, Avi Kivity wrote:

> On 08/26/2009 08:45 PM, Davide Libenzi wrote:
> > OK, if I get it correctly, there is one eventfd signaler (the device), and
> > one eventfd reader (the hypervisor), right?
> > Each hypervisor listens for multiple devices detecting state changes, and
> > associating the eventfd "line" to the IRQ number by some configuration
> > (ala PCI), right?
> >
>
> Yes. The PCI stuff happens in userspace, all the hypervisor sees is "this
> eventfd is IRQ 10". There may be multiple eventfds routed to one IRQ
> (corresponding to a shared IRQ line).

Ok, so why not using the eventfd counter as state?
On the device side:

void write_state(int sfd, int state) {
u64 cnt;

/* Clear the current state, sfd is in non-blocking mode */
read(sfd, &cnt, sizeof(cnt));
/* Writes new state */
cnt = 1 + !!state;
write(sfd, &cnt, sizeof(cnt));
}


On the hypervisor side:

int read_state(int sfd) {
u64 cnt;

read(sfd, &cnt, sizeof(cnt));
return state - 1;
}




- Davide




\
 
 \ /
  Last update: 2009-08-26 21:15    [W:0.088 / U:0.408 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site