linux-kernel - Re: [PATCH v2 1/2] cxl/cdat: Handle cdat table build errors

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Date: Mon, 8 Jan 2024 18:48:48 -0800
From: Ira Weiny <ira.weiny@...el.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>, Ira Weiny
	<ira.weiny@...el.com>
CC: fan <nifan.cxl@...il.com>, Dave Jiang <dave.jiang@...el.com>,
	<linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Huai-Cheng Kuo
	<hchkuo@...ry-design.com.tw>
Subject: Re: [PATCH v2 1/2] cxl/cdat: Handle cdat table build errors

Jonathan Cameron wrote:

[snip]

> > > > > 
> > > > > I did not go that far as I am unsure as well.    
> > > > Memory allocations in qemu don't fail (well if they do it crashes)
> > > > Side effect of using glib which makes for simpler cases.
> > > > https://docs.gtk.org/glib/func.malloc.html
> > > > 
> > > > There shouldn't even be any checks :(  I'll fix that up at somepoint
> > > > across all the CXL emulation.  Sometimes reviewers noticed and
> > > > we dropped it at earlier stages, but clearly didn't catch them all.
> > > > 
> > > > Which come to think of it is why this error condition is in practice
> > > > not actually buggy as the code won't ever manage to return -ENOMEM and
> > > > I don't think there are other error codes.    
> > > 
> > > Ah.  Ok but in that case I would say that build_cdat_table() should never
> > > return < 0 to be clear at this level what can happen.
> > > 
> > > Would you like a patch for that?  (/me assumes you dropped this patch)  
> > 
> > Probably needs to first rip out all the -ENOMEM returns that got into
> > the CXL code in general, then tidy up the return type to be unsigned.
> > 
> > If you want to do that it would be welcome!
> Actually.  Build_cdat_table() can return errors just not for this reason.
> 
> host_memory_backend_get_memory() can fail for example.

I must be on a different version because I don't see that.

>
> So original patch is good
> as is, just that the discussion of memory allocation failure threw me
> off and should be cleaned up separately.
> 

I did this testing on Fan's DCD version...  :-/  ... probably very out of
date.

Fan do you have a newer version than your 2023-11-16 branch?

Ira