linux-kernel - Re: [PATCH v4 0/3] irqfd support for arm/arm64

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Message-ID: <20141124094731.GH3401@cbox>
Date:	Mon, 24 Nov 2014 10:47:31 +0100
From:	Christoffer Dall <christoffer.dall@...aro.org>
To:	Eric Auger <eric.auger@...aro.org>
Cc:	eric.auger@...com, marc.zyngier@....com,
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
	kvm@...r.kernel.org, alex.williamson@...hat.com,
	joel.schopp@....com, kim.phillips@...escale.com, paulus@...ba.org,
	gleb@...nel.org, pbonzini@...hat.com, linux-kernel@...r.kernel.org,
	patches@...aro.org, will.deacon@....com,
	a.motakis@...tualopensystems.com, a.rigo@...tualopensystems.com,
	john.liuli@...wei.com, ming.lei@...onical.com, feng.wu@...el.com
Subject: Re: [PATCH v4 0/3] irqfd support for arm/arm64

On Sun, Nov 23, 2014 at 06:56:57PM +0100, Eric Auger wrote:
> This patch series enables irqfd on arm and arm64.
> 
> Irqfd framework enables to inject a virtual IRQ into a guest upon an
> eventfd trigger. User-side uses KVM_IRQFD VM ioctl to provide KVM with
> a kvm_irqfd struct that associates a VM, an eventfd, a virtual IRQ number
> (aka. the gsi). When an actor signals the eventfd (typically a VFIO
> platform driver), the kvm irqfd subsystem injects the gsi into the VM.
> 
> Resamplefd also is supported for level sensitive interrupts, ie. the
> user can provide another eventfd that is triggered when the completion
> of the virtual IRQ (gsi) is detected by the GIC.
> 
> The gsi must correspond to a shared peripheral interrupt (SPI), ie the
> GIC interrupt ID is gsi + 32.
> 
> The rationale behind not supporting PPI irqfd injection is that
> any device using a PPI would be a private-to-the-CPU device (timer for
> instance), so its state would have to be context-switched along with the
> VCPU and would require in-kernel wiring anyhow. It is not a relevant use
> case for irqfds.
> 
> this patch enables CONFIG_HAVE_KVM_EVENTFD and CONFIG_HAVE_KVM_IRQFD.
> 
> No IRQ routing table is used, enabling to remove CONFIG_HAVE_KVM_IRQCHIP
> 
> can be found at git://git.linaro.org/people/eric.auger/linux.git
> on branch irqfd_integ_v8
> 
> This work was tested with Calxeda Midway xgmac main interrupt with
> qemu-system-arm and QEMU VFIO platform device. Also irqfd was proven
> functional on several vhost-net prototypes.
> 
> v3 -> v4:
> - rebase on 3.18rc5
> - vgic dynamic instantiation brought new challenges:
>   handling of irqfd injection when vgic is not ready
> - unset of CONFIG_HAVE_KVM_IRQCHIP in a separate patch
> - add arm64 enable
> - vgic.c style modifications according to Christoffer comments
> 

There also seems to be a different split of the patches here?

We've probably also reached the point where you need to start rebasing
on Andre's GICv3 patches, which I expect will go in first.

Thanks,
-Christoffer
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