linux-kernel - Re: [PATCH v3 0/1] x86/hyperv: MSI parent domain conversion

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Message-ID: <aIJjrYne1VvGjBux@liuwe-devbox-ubuntu-v2.tail21d00.ts.net>
Date: Thu, 24 Jul 2025 16:47:41 +0000
From: Wei Liu <wei.liu@...nel.org>
To: Nam Cao <namcao@...utronix.de>
Cc: "K . Y . Srinivasan" <kys@...rosoft.com>,
	Nuno Das Neves <nunodasneves@...ux.microsoft.com>,
	Marc Zyngier <maz@...nel.org>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H . Peter Anvin" <hpa@...or.com>, linux-hyperv@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/1] x86/hyperv: MSI parent domain conversion

Nuno, can you please take a look at this patch?

On Fri, Jul 18, 2025 at 09:57:49PM +0200, Nam Cao wrote:
> The initial implementation of PCI/MSI interrupt domains in the hierarchical
> interrupt domain model used a shortcut by providing a global PCI/MSI
> domain.
> 
> This works because the PCI/MSI[X] hardware is standardized and uniform, but
> it violates the basic design principle of hierarchical interrupt domains:
> Each hardware block involved in the interrupt delivery chain should have a
> separate interrupt domain.
> 
> For PCI/MSI[X], the interrupt controller is per PCI device and not a global
> made-up entity.
> 
> Unsurprisingly, the shortcut turned out to have downsides as it does not
> allow dynamic allocation of interrupt vectors after initialization and it
> prevents supporting IMS on PCI. For further details, see:
> 
> https://lore.kernel.org/lkml/20221111120501.026511281@linutronix.de/
> 
> The solution is implementing per device MSI domains, this means the
> entities which provide global PCI/MSI domain so far have to implement MSI
> parent domain functionality instead.
> 
> This series converts the x86 hyperv driver to implement MSI parent domain.
> 
> Changes in v3:
> 
>   - Drop the merged patch
> 
>   - Rebase onto hyperv-fixes
> 
>  arch/x86/hyperv/irqdomain.c | 111 ++++++++++++++++++++++++------------
>  drivers/hv/Kconfig          |   1 +
>  2 files changed, 77 insertions(+), 35 deletions(-)
> 
> -- 
> 2.49.0
>