From: pbonzini@redhat•com (Paolo Bonzini)
To: linux-arm-kernel@lists•infradead.org
Subject: Extensions for KVM MSI related ioctls
Date: Mon, 13 Jul 2015 14:35:28 +0200 [thread overview]
Message-ID: <55A3B090.6090002@redhat.com> (raw)
In-Reply-To: <55A39231.4050904@arm.com>
On 13/07/2015 12:25, Andre Przywara wrote:
>
> For using MSIs in a guest when running on an ARM(64) system using a
> GICv3 interrupt controller we need to have a device ID available. On
> real hardware this information is sampled from the bus by the ITS part
> of the interrupt controller.
> To make this work for guests, we need to extend two ioctls which deal
> with MSIs: KVM_SIGNAL_MSI and KVM_SET_GSI_ROUTING.
>
> The idea that we sketched so far in [1] and [2] is to use a new
> capability (KVM_CAP_MSI_DEVID) to advertise both a flag bit for
> KVM_SIGNAL_MSI and a new type for KVM_SET_GSI_ROUTING.
>
> Since current kernels bail out on any flag value != 0 in KVM_SIGNAL_MSI,
> we need the new capability to tell userland about it in a reliable and
> portable way (to avoid hacks like #ifdef ARM && USES_IRQ_ROUTING in
> userland).
>
> For KVM_SET_GSI_ROUTING there was the idea of using the very same flag
> value in it's own flag field, but I find it saner to use a new routing
> type instead (KVM_IRQ_ROUTING_EXTENDED_MSI). Both approaches would
> piggy-back on the existing struct kvm_irq_routing_msi and re-purpose the
> pad field in there.
I think I prefer the flag. Offhand it sounds easier to add support for
it to non-ARM architectures, compared to KVM_IRQ_ROUTING_EXTENDED_MSI.
> Summarized:
> 1) Add a new KVM_CAP_MSI_DEVID to advertise the device ID extension.
> 2) Use a KVM_MSI_VALID_DEVID flag in KVM_SIGNAL_MSI to re-purpose part
> of struct kvm_msi.
These two sounds good.
Paolo
> 3) Add a new routing type KVM_IRQ_ROUTING_EXTENDED_MSI for
> KVM_SET_GSI_ROUTING to add device IDs in struct kvm_irq_routing_msi.
>
> Is that a sensible way to extend the KVM API?
next prev parent reply other threads:[~2015-07-13 12:35 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-13 10:25 Extensions for KVM MSI related ioctls Andre Przywara
2015-07-13 12:35 ` Paolo Bonzini [this message]
2015-07-13 13:32 ` Pavel Fedin
2015-07-13 14:24 ` Eric Auger
2015-07-13 14:29 ` Andre Przywara
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