linux-kernel - Re: [PATCH 0/3] MSI: Track device proxying when allocating MSIs

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Date:   Mon, 30 Nov 2020 13:14:26 +0000
From:   John Garry <john.garry@...wei.com>
To:     Marc Zyngier <maz@...nel.org>, <linux-kernel@...r.kernel.org>
CC:     Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 0/3] MSI: Track device proxying when allocating MSIs

On 29/11/2020 13:52, Marc Zyngier wrote:
> This series aims to plug a gap found with John's "managed interrupts
> for platform devices" series.
> 
> We have a couple of cases where we allocate MSIs for a device, but the
> endpoint generating the actual interrupts (let's call it the "logical
> device") isn't the one being seen generating the MSIs (the "effective
> device"):
> 
> - PCI devices behind a non transparent bridge
> - Devices attached to a wire-to-MSI bridge
> 
> For interrupt infrastructures such as the ITS (where the effective
> device ID is part of the translation), it is important decouple the
> lifetime of the effective device mapping from the interrupt allocation
> on behalf of the logical device. Yes, I have a headache too.
> 
> To achieve this split, let's tag the such allocations with a new flag
> that convey the fact that the effective device isn't the logical
> one. This mostly affects the platform-MSI subsystem.
> 
> Subsequent patches add handling of this new flag in the GICv3 ITS
> (though there may be scope for something more generic in the case of
> the last patch).

Hi Marc,

Tested-by: John Garry <john.garry@...wei.com>

Thanks!

> 
> Marc Zyngier (3):
>    platform-msi: Track shared domain allocation
>    irqchip/gic-v3-its: Tag ITS device as shared if allocating for a proxy
>      device
>    irqchip/gic-v3-its: Flag device allocation as proxied if behind a PCI
>      bridge
> 
>   drivers/base/platform-msi.c              |  7 +++++++
>   drivers/irqchip/irq-gic-v3-its-pci-msi.c | 11 ++++++++---
>   drivers/irqchip/irq-gic-v3-its.c         |  3 +++
>   include/asm-generic/msi.h                |  4 ++++
>   4 files changed, 22 insertions(+), 3 deletions(-)
>