linux-kernel - Re: [PATCH V1] PCI/MSI: Fix MSI hwirq truncation

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Date: Fri, 5 Jan 2024 09:02:06 -0800
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
To: Vidya Sagar <vidyas@...dia.com>, bhelgaas@...gle.com,
 rdunlap@...radead.org, ilpo.jarvinen@...ux.intel.com, tglx@...utronix.de
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, sagar.tv@...il.com
Subject: Re: [PATCH V1] PCI/MSI: Fix MSI hwirq truncation



On 1/5/2024 5:43 AM, 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 u32. 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 u64 before left shifting it to
> calculate hwirq number.

This seems like a bug fix. Why not add Fixes: tag?

Is this issue detected in a platform test? Maybe including the relevant
details about it will help reproduce the issue.

> 
> Signed-off-by: Vidya Sagar <vidyas@...dia.com>
> ---
>  drivers/pci/msi/irqdomain.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/msi/irqdomain.c b/drivers/pci/msi/irqdomain.c
> index c8be056c248d..cfd84a899c82 100644
> --- a/drivers/pci/msi/irqdomain.c
> +++ b/drivers/pci/msi/irqdomain.c
> @@ -61,7 +61,7 @@ static irq_hw_number_t pci_msi_domain_calc_hwirq(struct msi_desc *desc)
>  
>  	return (irq_hw_number_t)desc->msi_index |
>  		pci_dev_id(dev) << 11 |
> -		(pci_domain_nr(dev->bus) & 0xFFFFFFFF) << 27;
> +		((irq_hw_number_t)(pci_domain_nr(dev->bus) & 0xFFFFFFFF)) << 27;
>  }
>  
>  static void pci_msi_domain_set_desc(msi_alloc_info_t *arg,

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer