linux-kernel - Re: [PATCH V4] PCI/MSI: Fix MSI hwirq truncation

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Message-ID: <cfa789a0-5433-4e17-957f-a3e021a97eed@nvidia.com>
Date: Wed, 7 Feb 2024 12:29:29 +0530
From: Vidya Sagar <vidyas@...dia.com>
To: 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 V4] PCI/MSI: Fix MSI hwirq truncation

Hi Thomas / Bjorn,
Can you please guide me on getting this patch merged?

Thanks,
Vidya Sagar

On 1/31/2024 8:45 AM, Vidya Sagar wrote:
> Hi Thomas,
> Sorry to bother you.
> Would you mind giving an Ack to this patch?
> 
> Thanks,
> Vidya Sagar
> 
> On 1/23/2024 9:31 PM, Vidya Sagar wrote:
>> Hi Thomas,
>> Does this patch look fine to you?
>> If yes, would you mind giving an Ack?
>>
>> Thanks,
>> Vidya Sagar
>>
>> On 1/15/2024 7:26 PM, 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. Please note that this fixes the issue only
>>> on 64-bit systems and doesn't change the behavior in 32-bit systems i.e.
>>> the 32-bit systems continue to have the issue. Since the issue surfaces
>>> only if there are too many PCIe controllers in the system which usually
>>> is the case in modern server systems and they don't tend to run 32-bit
>>> kernels.
>>>
>>> Fixes: 3878eaefb89a ("PCI/MSI: Enhance core to support hierarchy 
>>> irqdomain")
>>> Tested-by: Shanker Donthineni <sdonthineni@...dia.com>
>>> Signed-off-by: Vidya Sagar <vidyas@...dia.com>
>>> ---
>>> V4:
>>> * Added extra information in the change log about the impact of this 
>>> patch
>>>    in a 32-bit system as suggested by Thomas
>>>
>>> V3:
>>> * Addressed review comments from Thomas Gleixner
>>> * Added Tested-By: Shanker Donthineni <sdonthineni@...dia.com>
>>>
>>> V2:
>>> * Added Fixes tag
>>>
>>>   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,