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From: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
To: <linux-cxl@vger.kernel.org>, <dan.j.williams@intel.com>
Subject: CXL/region :  commit reset of out of order region appears to succeed.
Date: Thu, 16 Mar 2023 17:14:41 +0000	[thread overview]
Message-ID: <20230316171441.0000205b@Huawei.com> (raw)

Ran into this whilst testing fix for QEMU uncommit handling.

To replicate.
1) Setup two regions on a direct connected Type 3 and commit them both.
2) Uncommit the first region once. (it fails with an out of order message)
   Note that from here on the sysfs commit attribute reads as 0.
3) Uncommit that first region again.  It appears to succeed.

Reason is easy to track down:
https://elixir.bootlin.com/linux/v6.3-rc2/source/drivers/cxl/core/region.c#L257

commit_store() of 0 unconditionally sets the state to CXL_CONFIG_RESET_PENDING

When the decoder reset fails, that is left set.
Hence next call drops straight through.

Whilst it's easy to 'fix' the superficial issue by reseting the state to the previous
value on error, I'm not sure that's sufficient or race free.

Hence report rather than a patch.  I can look into this in more depth, but
a few other things come before it in my list.

Thanks,

Jonathan

p.s. I hope to send the qemu fix for uncommit fairly soon.

             reply	other threads:[~2023-03-16 17:14 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-16 17:14 Jonathan Cameron [this message]
2023-06-17  0:26 ` CXL/region : commit reset of out of order region appears to succeed Dan Williams

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