[ofw] Support boot device in IB stack?

[James Yang]

Hi Tzachi,

The boot should be OK if #1 and #3 are resolved. In order to support
crashdump, the IB related code must be able to run at IRQL 31. It will
be good to know what functions are OK to run and what are not. By the
way, according to DDK, "Callers of KeAcquireSpinLock must be running at
IRQL <= DISPATCH_LEVEL."

There is no formal document on crashdump. The most important thing is
that it's running at IRQL 31, and multiple threading may not work at
this time.

iSCSI is one of the solutions, but we also have to support vhba
directly. And in order to get MS WHQL for vhba, we must support
crashdump. Do you get any request to support crashdump on iSCSI/ipoib?

Thanks,
James 

-----Original Message-----
From: Tzachi Dar [mailto:tzachid at mellanox.co.il] 
Sent: Wednesday, February 11, 2009 12:55 AM
To: James Yang; ofw at lists.openfabrics.org
Subject: RE: [ofw] Support boot device in IB stack?

Hi James,

As for 1,3 this are technical changes that can easily be done.

Issue #2 seems much more problematic to me.
First I must say that I haven't studied the topic thoroughly, so I might
be getting a wrong impression of the entire issue.
One more thing to start with, is that I'm not sure that this request is
a must. What I mean by that is that booting will take place just fine.
The one thing that will not work is creating a crash dump file later.

In any case, spinlocks don't really have a problem with higher IRQL (the
way I understand it), but many other commands have. So if the code is
only trying to send/receive data with qps that are open I guess that
things should work. Trying to open new QPs will not work (we have to
wait). Please also note that there are only about 5 commands that can be
called from IRQL>DISPATCH_LEVEL.

Can you please send a reference to the document that says what are the
demands after the system has crashed?

Another question is this, will booting using iSCSI be a better option
for you? (not that it was done using ipoib).

Thanks
Tzachi

> -----Original Message-----
> From: ofw-bounces at lists.openfabrics.org 
> [mailto:ofw-bounces at lists.openfabrics.org] On Behalf Of James Yang
> Sent: Tuesday, February 10, 2009 11:31 PM
> To: ofw at lists.openfabrics.org
> Subject: [ofw] Support boot device in IB stack?
> 
> Hi,
> 
> We would like to support boot device especially SAN boot over 
> IB. So far I can see the following issues in current code:
> 1) Many functions are page-able. If these functions are 
> running at boot or shut down time, the disk may not be ready, 
> the paging won't work.
> 2) Spinlock may not work for crashdump, whose 
> IRQL>DISPATCH_LEVEL. Any other functions need to be changed 
> when IRQL>DISPATCH_LEVEL?
> 3) All related drivers should be boot start driver.
> 
> Are there any other potential problem? Is there any plan to 
> support SAN boot?
> 
> Please advice.
> 
> Thanks,
> James
> 
> 
> 
> 
> 
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