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Message-ID: <20090728175435.GA21549@redhat.com>
Date: Tue, 28 Jul 2009 20:54:35 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: davidel@...ilserver.org, avi@...hat.com, gleb@...hat.com,
kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH-RFC 0/2] eventfd: new EFD_STATE flag
Davide, all,
This RFC series implements a new EFD_STATE flag for eventfd.
When set, this changes eventfd behaviour in the following way:
- write simply stores the value written, and is always non-blocking
- read unblocks when the value written changes, and
returns the value written
Motivation: we'd like to use eventfd in qemu to pass interrupts from
(emulated or assigned) devices to guest. For level interrupts, the
counter supported currently by eventfd is not a good match: we really
need to set interrupt to a level, typically 0 or 1, wake the guest if
there was a change and and give the guest ability to see the last value
written.
Does extending eventfd in this way make sense? Please comment.
Michael S. Tsirkin (2):
eventfd: reorganize the code to simplify new flags
eventfd: EFD_STATE flag
fs/eventfd.c | 83 +++++++++++++++++++++++++++++++++++++++--------
include/linux/eventfd.h | 3 +-
2 files changed, 71 insertions(+), 15 deletions(-)
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