From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: AHCI question Date: Tue, 23 Nov 2010 10:54:36 -0500 Message-ID: <20101123155436.GA2786@dumpdata.com> References: <20101122164252.GC21254@dumpdata.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Kamala Narasimhan Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On Mon, Nov 22, 2010 at 12:07:58PM -0500, Kamala Narasimhan wrote: > It is a bare minimal driver in Xen (under development) which is > invoked upon a system crash to persist crash dump data to disk by > issuing commands through the pre-programmed HBA registers. Unlike a > full fledged AHCI driver, we do not initialize the very many memory > regions used to communicate between the device and the system software > as in our case the dom0 would have already done all that. We simply > map those memory regions that dom0 has already setup and issue > commands to copy data to disk. And that issuing of command part is > not succeeding as I would expect. I think you are better of asking on the ahci-devel, and as well folks on the kdump mailing list as they had to wrestle with these kinds of issues already. Thought .. why not use the kdump kernel? >=20 > Kamala >=20 > On Mon, Nov 22, 2010 at 11:42 AM, Konrad Rzeszutek Wilk > wrote: > > On Mon, Nov 22, 2010 at 09:51:26AM -0500, Kamala Narasimhan wrote: > >> I am writing a polled mode Xen AHCI driver to collect some minimal > > > > What is a 'Xen AHCI' driver? > > > >> information after a system crash. =A0As 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. =A0I a= m > >> also not setting up interrupts etc. as the driver is used in polled > >> mode. =A0I simply map the abar and other memory regions associated w= ith > >> the device that dom0 has already setup and write to it/read from it = as > >> needed. > >> > >> After a crash, within the Xen AHCI driver I am able to get to the pc= i > >> space for the device, get valid HBA registers, mapping etc. works bu= t > >> 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) fo= r > >> 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. =A0Thanks. > >> > >> Kamala > >> > >> _______________________________________________ > >> Xen-devel mailing list > >> Xen-devel@lists.xensource.com > >> http://lists.xensource.com/xen-devel > > >=20 > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel