linux-kernel - Re: [PATCH v10 3/7] PCI: endpoint: pci-ep-msi: Add MSI address/data pair mutable check

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Message-ID: <87ttbiqnq8.ffs@tglx>
Date: Thu, 05 Dec 2024 14:10:55 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Frank Li <Frank.Li@....com>, Manivannan Sadhasivam
 <manivannan.sadhasivam@...aro.org>, Krzysztof Wilczyński
 <kw@...ux.com>,
 Kishon Vijay Abraham I <kishon@...nel.org>, Bjorn Helgaas
 <bhelgaas@...gle.com>, Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>,
 Anup Patel <apatel@...tanamicro.com>, Marc Zyngier <maz@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
 imx@...ts.linux.dev, Niklas Cassel <cassel@...nel.org>,
 dlemoal@...nel.org, jdmason@...zu.us,
 linux-arm-kernel@...ts.infradead.org, Frank Li <Frank.Li@....com>
Subject: Re: [PATCH v10 3/7] PCI: endpoint: pci-ep-msi: Add MSI address/data
 pair mutable check

On Wed, Dec 04 2024 at 18:25, Frank Li wrote:
> Some MSI controller change address/data pair when irq_set_affinity().
> Current PCI endpoint can't support this type MSI controller. So add flag
> MSI_FLAG_MUTABLE in include/linux/msi.h and check it when allocate
> doorbell.

Q: Who is going to annotate the affected domains with that flag?

A: Nobody.

Q: What's the value of the flag?

A: Zero, as as it prevents exactly nothing.

You want a MSI_FLAG_MSG_IMMUTABLE and set that on the domains which
provide it. That way you ensure that someone looked at the domain to
validate it.

Thanks,

        tglx