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From: Paolo Bonzini <pbonzini@redhat.com>
To: Alex Williamson <alex.williamson@redhat.com>,
	Micah Morton <mortonm@chromium.org>
Cc: kvm@vger.kernel.org, jmattson@google.com
Subject: Re: [RFC PATCH] KVM: Add module for IRQ forwarding
Date: Wed, 13 May 2020 09:02:16 +0200	[thread overview]
Message-ID: <92fd66eb-68e7-596f-7dd1-f1c190833be4@redhat.com> (raw)
In-Reply-To: <20200512111440.15caaca2@w520.home>

On 12/05/20 19:14, Alex Williamson wrote:
> But why not assign the individual platform devices via vfio-platform
> rather than assign the i2c controller via vfio-pci and then assembling
> the interrupts from those sub-devices with this ad-hoc interface?  An
> emulated i2c controller in the guest could provide the same discovery
> mechanism as is available in the host.

I agree.  I read the whole discussion, but I still don't understand why
this is not using vfio-platform.

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?

(Finally, in the past we were doing device assignment tasks within KVM
and it was a bad idea.  Anything you want to do within KVM with respect
to device assignment, someone else will want to do it from bare metal.
virt/lib/irqbypass.c is a special case because it's an IOMMU feature
that is designed to work in concert with VMX posted interrupts and SVM
AVIC, so in guest mode only).

Paolo


  reply	other threads:[~2020-05-13  7:02 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 [this message]
2020-05-13 14:34     ` Alex Williamson
2020-05-13 15:23       ` Paolo Bonzini
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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