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From: Paolo Bonzini <pbonzini@redhat.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Micah Morton <mortonm@chromium.org>,
	kvm@vger.kernel.org, jmattson@google.com
Subject: Re: [RFC PATCH] KVM: Add module for IRQ forwarding
Date: Wed, 13 May 2020 17:23:19 +0200	[thread overview]
Message-ID: <8c0bfeb7-0d08-db74-3a23-7a850f301a2a@redhat.com> (raw)
In-Reply-To: <20200513083401.11e761a7@x1.home>

On 13/05/20 16:34, Alex Williamson wrote:
>> Alternatively, if you assign the i2c controller, I don't understand why
>> the guest doesn't discover interrupts on its own.  Of course you need to
>> tell the guest about the devices in the ACPI tables, but why is this new
>> concept necessary?
>
> the interrupt for this sub-device is unrelated to the PCI
> controller device, it's an entirely arbitrary (from our perspective)
> relationship described via ACPI.

Ok, that's what I was missing.

> We could potentially use device specific interrupts to expose this via
> the controller device, but then vfio-pci needs to learn how to
> essentially become an i2c controller to enumerate the sub-devices and
> collect external dependencies.  This is not an approach I've embraced
> versus the alternative of the host i2c driver claiming the PCI
> controller, enumerating the sub-devices, and binding the resulting
> device, complete with built-in interrupt support via vfio-platform.

I agree that's the way to go.

Perhaps adding arbitrary non-PCI interrupts, i.e. neither INTX nor
MSI(-X), to vfio-pci could be acceptable.  However, the device claim
must claim them, and that seems hard to do when you rebind the PCI
device to pci-stub.

Paolo


  reply	other threads:[~2020-05-13 15:23 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-11 22:00 [RFC PATCH] KVM: Add module for IRQ forwarding Micah Morton
2020-05-12  1:45 ` kbuild test robot
2020-05-12 17:14 ` Alex Williamson
2020-05-13  7:02   ` Paolo Bonzini
2020-05-13 14:34     ` Alex Williamson
2020-05-13 15:23       ` Paolo Bonzini [this message]
2020-05-13 19:10         ` Micah Morton
2020-05-13 22:05           ` Paolo Bonzini
2020-05-14 17:44             ` Micah Morton
2020-05-14 21:17               ` Paolo Bonzini
2020-05-14 22:43                 ` Alex Williamson
2020-05-15 20:30                   ` Micah Morton
2020-06-03 18:23                     ` [PATCH] vfio: PoC patch for printing IRQs used by i2c devices Micah Morton
2020-06-09 20:19                       ` Micah Morton
2020-06-19 18:51                         ` Alex Williamson
2020-06-19 20:00                           ` Micah Morton
2020-06-22 21:59                             ` Micah Morton
2020-05-15 10:11               ` [RFC PATCH] KVM: Add module for IRQ forwarding Auger Eric
2020-05-15 16:39                 ` Micah Morton
2020-05-13 21:52     ` Micah Morton

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