linux-kernel - Re: [PATCH 1/1] genirq/msi: Dynamic remove/add stroage adapter hits EEH

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Message-ID: <874izo3x60.ffs@tglx>
Date: Thu, 20 Mar 2025 09:48:23 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Wen Xiong <wenxiong@...ux.ibm.com>
Cc: linux-kernel@...r.kernel.org, gjoyce@...ux.ibm.com,
 linux-pci@...r.kernel.org, Bjorn Helgaas <helgaas@...nel.org>,
 linux-scsi@...r.kernel.org
Subject: Re: [PATCH 1/1] genirq/msi: Dynamic remove/add stroage adapter hits
 EEH

On Thu, Mar 20 2025 at 09:23, Thomas Gleixner wrote:
> On Wed, Mar 19 2025 at 21:58, Wen Xiong wrote:
>> We don't see the issue without dynamically remove/add operation.
>> There is a small window which irqbalance daemon kicks in during device
>> reset. So it took about over 6 hours to recreate the issue when doing
>> remove/add loop operation.
>
> Sure. You need a loop to hit the window. And it does not matter whether
> it's the probe or the remove which triggers it. Fact is that the reset
> wipes out the config space, which means that any read from the config
> space between reset and restore will return garbage. That problem is not
> restricted to the interrupt code. It's a general problem.

After looking at the code again, it's a problem in the remove()
function:

__ipr_remove()
  ipr_initiate_ioa_bringdown() 
    // resets device
    restore_config_space()
  ....
  ipr_free_all_resources()
    free_irqs()

So yes, it's not probe(). But the question is pretty much the same.

Why is a reset issued while the driver is fully operational and
resources are still in use?

Don't even think about telling me that this is a problem of the MSI
interrupt rework. It is not. It's been broken forever.

You _cannot_ pull the rung under a fully operational driver and expect
that all involved parts will just magically handle this gracefully.

What about tearing down resources first and then issuing the reset?

Thanks,

        tglx