From: Avi Kivity <avi@redhat.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: mst@redhat.com, gleb@redhat.com, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, jan.kiszka@siemens.com
Subject: Re: [PATCH v7 2/2] kvm: KVM_EOIFD, an eventfd for EOIs
Date: Mon, 06 Aug 2012 13:17:12 +0300 [thread overview]
Message-ID: <501F99A8.9050006@redhat.com> (raw)
In-Reply-To: <20120724204320.21081.32333.stgit@bling.home>
On 07/24/2012 11:43 PM, Alex Williamson wrote:
> This new ioctl enables an eventfd to be triggered when an EOI is
> written for a specified irqchip pin. The first user of this will
> be external device assignment through VFIO, using a level irqfd
> for asserting a PCI INTx interrupt and this interface for de-assert
> and notification once the interrupt is serviced.
>
> Here we make use of the reference counting of the _irq_source
> object allowing us to share it with an irqfd and cleanup regardless
> of the release order.
The name is slightly misleading. eoifd doesn't trigger on EOI (which is
an APIC->IOAPIC interface) but rather when an interrupt controller
resamples an input line. This happens for the IOAPIC when an EOI is
received for a vector that is configured for level interrupts and not
masked, or similarly for a PIC (but this is not triggered by an APIC EOI).
It's not a huge difference, but let's document it.
>
> +4.77 KVM_EOIFD
> +
> +Capability: KVM_CAP_EOIFD
> +Architectures: x86
> +Type: vm ioctl
> +Parameters: struct kvm_eoifd (in)
> +Returns: 0 on success, < 0 on error
> +
> +KVM_EOIFD allows userspace to receive interrupt EOI notification
> +through an eventfd. kvm_eoifd.fd specifies the eventfd used for
> +notification. KVM_EOIFD_FLAG_DEASSIGN is used to de-assign an eoifd
> +once assigned. KVM_EOIFD also requires additional bits set in
> +kvm_eoifd.flags to bind to the proper interrupt line. The
> +KVM_EOIFD_FLAG_LEVEL_IRQFD indicates that kvm_eoifd.key is provided
> +and is a key from a level triggered interrupt (configured from
> +KVM_IRQFD using KVM_IRQFD_FLAG_LEVEL). The EOI notification is bound
> +to the same GSI and irqchip input as the irqfd. Both kvm_eoifd.key
> +and KVM_EOIFD_FLAG_LEVEL_IRQFD must be specified on assignment and
> +de-assignment of KVM_EOIFD. A level irqfd may only be bound to a
> +single eoifd. KVM_CAP_EOIFD_LEVEL_IRQFD indicates support of
> +KVM_EOIFD_FLAG_LEVEL_IRQFD.
Why do we need to couple eoifd and irqfd?
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2012-08-06 10:17 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-24 20:43 [PATCH v7 0/2] kvm: level irqfd and new eoifd Alex Williamson
2012-07-24 20:43 ` [PATCH v7 1/2] kvm: Extend irqfd to support level interrupts Alex Williamson
2012-07-29 15:01 ` Michael S. Tsirkin
2012-07-30 16:06 ` Alex Williamson
2012-07-24 20:43 ` [PATCH v7 2/2] kvm: KVM_EOIFD, an eventfd for EOIs Alex Williamson
2012-07-29 14:54 ` Michael S. Tsirkin
2012-07-30 16:22 ` Alex Williamson
2012-07-31 0:01 ` Michael S. Tsirkin
2012-07-31 0:26 ` Alex Williamson
2012-07-31 0:36 ` Michael S. Tsirkin
2012-07-31 1:12 ` Alex Williamson
2012-08-01 19:06 ` Alex Williamson
2012-08-12 7:49 ` Michael S. Tsirkin
2012-08-13 16:48 ` Alex Williamson
2012-08-13 16:59 ` Michael S. Tsirkin
2012-08-13 18:17 ` Alex Williamson
2012-08-13 19:50 ` Michael S. Tsirkin
2012-08-13 20:48 ` Alex Williamson
2012-08-13 21:50 ` Michael S. Tsirkin
2012-08-13 22:22 ` Alex Williamson
2012-08-13 22:52 ` Michael S. Tsirkin
2012-08-14 10:10 ` Gleb Natapov
2012-08-14 10:13 ` Gleb Natapov
2012-08-02 8:42 ` Michael S. Tsirkin
2012-08-06 10:17 ` Avi Kivity [this message]
2012-08-06 10:38 ` Avi Kivity
2012-08-06 10:40 ` Avi Kivity
2012-08-09 19:26 ` Alex Williamson
2012-08-12 8:36 ` Avi Kivity
2012-08-13 21:34 ` Alex Williamson
2012-08-13 22:06 ` Michael S. Tsirkin
2012-08-13 22:41 ` Alex Williamson
2012-08-13 23:00 ` Michael S. Tsirkin
2012-08-14 3:09 ` Alex Williamson
2012-08-14 8:35 ` Michael S. Tsirkin
2012-08-14 21:28 ` Alex Williamson
2012-08-12 9:33 ` Michael S. Tsirkin
2012-08-13 21:23 ` Alex Williamson
2012-08-13 22:00 ` Michael S. Tsirkin
2012-08-14 12:35 ` Avi Kivity
2012-08-14 14:50 ` Michael S. Tsirkin
2012-08-14 22:01 ` Alex Williamson
2012-08-14 23:04 ` Michael S. Tsirkin
2012-08-14 23:26 ` Alex Williamson
2012-08-15 13:09 ` Avi Kivity
2012-08-12 7:53 ` Michael S. Tsirkin
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