[ofw] typical values for ci_umv_buf_t

[Leonid Keller]

> (Fab) Are there cases where there's a pre-IOCTL call but not a
post-IOCTL call ?
There are in the existing code.
It is used when the UVP has done all the work in the pre- call and is
not interested in ioctl.
The Uvp shows that by returning IB_VERBS_PROCESSING_DONE from the pre-
call.
(see mlnx_ual_av.c)

> -----Original Message-----
> From: ofw-bounces at lists.openfabrics.org 
> [mailto:ofw-bounces at lists.openfabrics.org] On Behalf Of Sean Hefty
> Sent: Thursday, March 13, 2008 12:54 AM
> To: 'Fab Tillier'; ofw at lists.openfabrics.org
> Subject: RE: [ofw] typical values for ci_umv_buf_t
> 
> >Are there cases where there's a pre-IOCTL call but not a post-IOCTL 
> >call?  I would expect things to go poorly if you use 
> uninitialized memory.
> >Specifically, the kernel proxy code that marshals the 
> p_inout_buf would 
> >detect a bad pointer if input_size or output_size where non-zero and 
> >p_inout_buf was non-zero too (unless you get 'lucky' and 
> p_inout_buf is 
> >a valid pointer in the app's memory space, and input_size and 
> >output_size are valid for that buffer.)
> 
> I'm trying to understand the requirements of the userspace 
> verbs library and the kernel HCA driver, not IBALs 
> requirements.  For example, how the ci_umv_buf_t data is 
> conveyed to or from the kernel is an implementation issue.  
> Command is only passed to the kernel, and status is only 
> returned from the kernel.  I would expect the verbs library 
> to ignore command in a post() call, and the kernel driver to 
> ignore status.
> 
> >>Does this imply that the HCA driver supports being called from an 
> >>arbitrary thread context, or must it be called from the 
> user's thread context directly?
> >
> >IBAL has the requirement that all IOCTLs be done in the 
> context of the 
> >application's thread.  This allows it to perform memory registration 
> >and other such calls where being in the app's thread context is 
> >required.  For other requests, if things get pushed to a 
> async callback 
> >work item, you can't dereference embedded pointers in the 
> p_inout_buf.  
> >So whether you can be called from arbitrary context depends 
> on the usage of the p_inout_buf.
> 
> Again, I'm asking about the requirements from the perspective 
> of the HCA driver.
> 
> - Sean
> 
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