netdev - Re: [PATCH 1/2] PCI/MSI: Add MSIX option to write to ENTRY

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Message-ID: <5a580609-aa5e-4153-b8dd-a6751af72685@yahoo.com>
Date: Mon, 20 Jan 2025 06:38:19 -0600
From: Dullfire <dullfire@...oo.com>
To: Paolo Abeni <pabeni@...hat.com>, "David S . Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
 Jacob Keller <jacob.e.keller@...el.com>, Simon Horman <horms@...nel.org>,
 Thomas Gleixner <tglx@...utronix.de>, Mostafa Saleh <smostafa@...gle.com>,
 Marc Zyngier <maz@...nel.org>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Cc: stable@...r.kernel.org
Subject: Re: [PATCH 1/2] PCI/MSI: Add MSIX option to write to ENTRY_DATA
 before any reads

On 11/21/24 04:28, Paolo Abeni wrote:
> On 11/21/24 10:22, Dullfire wrote:
>> On 11/21/24 02:55, Paolo Abeni wrote:
>>> On 11/18/24 00:48, dullfire@...oo.com wrote:
>>>> From: Jonathan Currier <dullfire@...oo.com>
>>>>
>>>> Commit 7d5ec3d36123 ("PCI/MSI: Mask all unused MSI-X entries")
>>>> introduces a readl() from ENTRY_VECTOR_CTRL before the writel() to
>>>> ENTRY_DATA. This is correct, however some hardware, like the Sun Neptune
>>>> chips, the niu module, will cause an error and/or fatal trap if any MSIX
>>>> table entry is read before the corresponding ENTRY_DATA field is written
>>>> to. This patch adds an optional early writel() in msix_prepare_msi_desc().
>>> Why the issue can't be addressed into the relevant device driver? It
>>> looks like an H/W bug, a driver specific fix looks IMHO more fitting.
>>
>> I considered this approach, and thus asked about it in the mailing lists here:
>> https://lore.kernel.org/sparclinux/7de14cca-e2fa-49f7-b83e-5f8322cc9e56@yahoo.com/T/
> 
> I forgot about such thread, thank you for the reminder. Since the more
> hackish code is IRQ specific, if Thomas is fine with that, I'll not oppose.
> 
>>> A cross subsystem series, like this one, gives some extra complication
>>> to maintainers.
> 
> The niu driver is not exactly under very active development, I guess the
> whole series could go via the IRQ subsystem, if Thomas agrees.
> 
> Cheers,
> 
> Paolo
> 

Thomas, does this work for you, or is there something else you would to see in this series?

Sincerely,
Jonathan Currier