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[Xen-devel] AHCI question

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] AHCI question
From: Kamala Narasimhan <kamala.narasimhan@xxxxxxxxx>
Date: Mon, 22 Nov 2010 09:51:26 -0500
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I am writing a polled mode Xen AHCI driver to collect some minimal
information after a system crash.  As dom0 would have initialized and
used the HBA before we enter the crashing code path, I am not doing
any kind of device initialization within the Xen AHCI driver.  I am
also not setting up interrupts etc. as the driver is used in polled
mode.  I simply map the abar and other memory regions associated with
the device that dom0 has already setup and write to it/read from it as

After a crash, within the Xen AHCI driver I am able to get to the pci
space for the device, get valid HBA registers, mapping etc. works but
the HBA does not respond back after I issue a command for execution.
In specific, after I set the port x command issue register (pxci) for
the free slot, that slot is not getting cleared as it should after a
command execution.

As an experiment to see if anything at all works with respect to
setting/resetting port registers, I simply decided to stop/start the
HBA command engine by setting the ST bit in the command register
(PxCMD) to 0 and then checking if CR, FR bit etc. in PxCMD are reset
by HBA after a ST reset but they remain set.

I am hoping someone with AHCI experience might be able to shed some
light as to why the HBA is not responding as it should.  Thanks.


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