linux-kernel - [v4] genirq/msi: Add the address and data that show MSI/MSIX

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Message-Id: <20250303121008.309265-1-18255117159@163.com>
Date: Mon,  3 Mar 2025 20:10:08 +0800
From: Hans Zhang <18255117159@....com>
To: tglx@...utronix.de
Cc: manivannan.sadhasivam@...aro.org,
	kw@...ux.com,
	kwilczynski@...nel.org,
	bhelgaas@...gle.com,
	Frank.Li@....com,
	cassel@...nel.org,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Hans Zhang <18255117159@....com>
Subject: [v4] genirq/msi: Add the address and data that show MSI/MSIX

The debug_show() callback function is implemented in the MSI core code.
And assign it to the domain ops::debug_show() creation.

When debugging MSI-related hardware issues (e.g., interrupt delivery
failures), developers currently need to either:
1. Recompile kernel with dynamic debug for tracing msi_desc.
2. Manually read device registers through low-level tools.

Both approaches become challenging in production environments where
dynamic debugging is often disabled.

This patch proposes to expose MSI address_hi/address_lo and msg_data in
`/sys/kernel/debug/irq/irqs/<msi_irq_num>`. These fields are critical to:
- Verify if MSI configuration matches hardware programming
- Diagnose interrupt routing errors (e.g., mismatched destination ID)
- Validate remapping behavior in virtualized environments

The information is already maintained in msi_desc and irq_data structures