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: <Z1G/CwFvO/aBLBe8@lizhi-Precision-Tower-5810>
Date: Thu, 5 Dec 2024 09:56:11 -0500
From: Frank Li <Frank.li@....com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: 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>,
	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
Subject: Re: [PATCH v10 3/7] PCI: endpoint: pci-ep-msi: Add MSI address/data
 pair mutable check

On Thu, Dec 05, 2024 at 02:10:55PM +0100, Thomas Gleixner wrote:
> 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.

Okay, at beginning I think most MSI controller is immutable. So I use
MSI_FLAG_MSG_MUTABLE.

It is fine change to MSI_FLAG_MSG_IMMUTABLE.

Frank

>
> Thanks,
>
>         tglx