Re: [PATCH] cxl: Perform NULL check for 'cxl_afu *' at various places in cxl

On 09/03/18 13:59, Vaibhav Jain wrote:

Thanks for looking into this patch Andrew,

Andrew Donnellan [off-list ref] writes:

quoted

On 08/03/18 21:05, Vaibhav Jain wrote:

quoted

It is possible for a CXL card to have a valid PSL but no valid
AFUs. When this happens we have a valid instance of 'struct cxl'
representing the adapter but with its member 'struct cxl_afu *cxl[]'
as empty. Unfortunately at many placed within cxl code (especially
during an EEH) the elements of this array are passed on to various
other cxl functions. Which may result in kernel oops/panic when this
'struct cxl_afu *' is dereferenced.

So this patch puts a NULL check at the beginning of various cxl
functions that accept 'struct cxl_afu *' as a formal argument and are
called from with a loop of the form:

         for (i = 0; i < adapter->slices; i++) {
         	   	afu = adapter->afu[i];
		/* call some function with 'afu' */
	}

Surely in this case adapter->slices should be 0?

Not necessarily, as adapter->slice doesnt take into account AFUs that
fail to init. I saw this issue in one specific case were the only slice
on the card had issued with the AFU descriptor caused CXL init of that
AFU to fail.

Ah OK, makes sense.


-- 
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan@au1.ibm.com  IBM Australia Limited