linux-kernel - Re: [PATCH v11 3/7] PCI: endpoint: pci-ep-msi: Add MSI address/data pair mutable check

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Message-ID: <87h67cprc7.ffs@tglx>
Date: Mon, 09 Dec 2024 20:51:52 +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 v11 3/7] PCI: endpoint: pci-ep-msi: Add MSI address/data
 pair mutable check

Frank!

On Mon, Dec 09 2024 at 12:48, 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_MSG_IMMUTABLE in include/linux/msi.h, set this flags in ARM GIC
> ITS MSI controller and check it when allocate doorbell.
>
> Signed-off-by: Frank Li <Frank.Li@....com>
> ---
> Change from v9 to v11
> - new patch
> ---
>  drivers/irqchip/irq-gic-v3-its-msi-parent.c | 1 +
>  drivers/pci/endpoint/pci-ep-msi.c           | 8 ++++++++
>  include/linux/msi.h                         | 2 ++

This is not how it works and I explained that you to more than once in
the past.

The change to the interrupt code is standalone and has nothing to do
with PCI endpoint. The latter is just a user of this.

So this want's to be split into several patches:

   1) add the new flag and a helper function which checks for the flag.

   2) add the flag to GICv3 ITS with a proper explanation

   3) Check for it in the PCI endpoint code

>  
> +	if (!dom->msi_parent_ops)
> +		return -EINVAL;

irq_domain_is_msi_parent()

> +	if (!(dom->msi_parent_ops->supported_flags & MSI_FLAG_MSG_IMMUTABLE)) {

Want's a helper.

Thanks,

        tglx