linux-kernel - Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support

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Message-ID: <20151006173846-mutt-send-email-mst@redhat.com>
Date:	Tue, 6 Oct 2015 17:46:31 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Avi Kivity <avi@...lladb.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Vlad Zolotarov <vladz@...udius-systems.com>,
	linux-kernel@...r.kernel.org, hjk@...sjkoch.de, corbet@....net,
	bruce.richardson@...el.com, avi@...udius-systems.com,
	gleb@...udius-systems.com, stephen@...workplumber.org,
	alexander.duyck@...il.com
Subject: Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support

On Mon, Oct 05, 2015 at 11:28:03AM +0300, Avi Kivity wrote:
> Eventfd is a natural enough representation of an interrupt; both kvm and
> vfio use it, and are also able to share the eventfd, allowing a vfio
> interrupt to generate a kvm interrupt, without userspace intervention, and
> one day without even kernel intervention.

eventfd without kernel intervention sounds unlikely.

kvm might configure the cpu such that an interrupt will not trigger a
vmexit.  eventfd seems like an unlikely interface to do that: with the
eventfd, device triggering it has no info about the interrupt so it
can't send it to the correct VM.

-- 
MST
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