linux-kernel - Re: [PATCH V3] PCI/MSI: Fix MSI hwirq truncation

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Date: Fri, 12 Jan 2024 16:53:26 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Vidya Sagar <vidyas@...dia.com>, bhelgaas@...gle.com,
 rdunlap@...radead.org, ilpo.jarvinen@...ux.intel.com,
 jiang.liu@...ux.intel.com
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
 treding@...dia.com, jonathanh@...dia.com, sdonthineni@...dia.com,
 kthota@...dia.com, mmaddireddy@...dia.com, vidyas@...dia.com,
 sagar.tv@...il.com
Subject: Re: [PATCH V3] PCI/MSI: Fix MSI hwirq truncation

On Thu, Jan 11 2024 at 10:58, Vidya Sagar wrote:
> While calculating the hwirq number for an MSI interrupt, the higher
> bits (i.e. from bit-5 onwards a.k.a domain_nr >= 32) of the PCI domain
> number gets truncated because of the shifted value casting to return
> type of pci_domain_nr() which is 'int'. This for example is resulting
> in same hwirq number for devices 0019:00:00.0 and 0039:00:00.0.
>
> So, cast the PCI domain number to 'irq_hw_number_t' before left shifting
> it to calculate hwirq number.

This still does not explain that this fixes it only on 64-bit platforms
and why we don't care for 32-bit systems.