Re: [PATCH v8 4/5] hw/mem/cxl-type3: Add CXL CDAT Data Object Exchange

[Jonathan Cameron via <qemu-devel@nongnu.org>]

On Thu, 13 Oct 2022 13:32:26 -0400
Gregory Price <gregory.price@memverge.com> wrote:

> If you're expecting this to be dynamic in size in the future, then maybe
> what we really want here is a function
> 
> static int ct3_get_cdat_size(CXLType3Dev ct3d) {
>     /* TODO: Dynamic sizing calculations */
>     return CT3_CDAT_NUM_ENTRIES;
> }

Perhaps, though that suffers from lack of locality and clearly
flagging that the enum is definitely not global.

Anyhow, lets argue that mechanism when it's needed :)

Jonathan

> 
> 
> On Thu, Oct 13, 2022 at 06:21:44PM +0100, Jonathan Cameron wrote:
> > On Thu, 13 Oct 2022 13:09:26 -0400
> > "Michael S. Tsirkin" <mst@redhat.com> wrote:
> >   
> > > On Thu, Oct 13, 2022 at 12:26:58PM -0400, Gregory Price wrote:  
> > > > Other than the nitpicks below, lgtm.  Not sure if you need a sign off
> > > > from me given the contributions:
> > > > 
> > > > Signed-off-by: Gregory Price <gregory.price@memverge.com>
> > > >     
> > > > > +/* If no cdat_table == NULL returns number of entries */
> > > > > +static int ct3_build_cdat_entries_for_mr(CDATSubHeader **cdat_table,
> > > > > +                                         int dsmad_handle, MemoryRegion *mr)
> > > > > +{
> > > > > +    enum {
> > > > > +        DSMAS,
> > > > > +        DSLBIS0,
> > > > > +        DSLBIS1,
> > > > > +        DSLBIS2,
> > > > > +        DSLBIS3,
> > > > > +        DSEMTS,
> > > > > +        NUM_ENTRIES
> > > > > +    };    
> > > > // ...    
> > > > > +    if (!cdat_table) {
> > > > > +        return NUM_ENTRIES;
> > > > > +    }    
> > > > 
> > > > the only thing that i would recommend is making this enum global (maybe
> > > > renaming them CT3_CDAT_[ENTRY_NAME]) and using CT3_CDAT_NUM_ENTRIES
> > > > directly in the function that allocates the cdat buffer itself.    
> > > 
> > > 
> > > Yes I think I agree here.  
> > 
> > Ok, seems a consensus against having this local.
> > 
> > I can do this for now and then revisit if / when things become more complex
> > and this becomes not global.  I guess a potential case of premature flexibility.
> > 
> > Jonathan
> >   
> > >   
> > > > I do
> > > > understand the want to keep the enum and the code creating the entries
> > > > co-located though, so i'm just nitpicking here i guess.
> > > > 
> > > > Generally I dislike the pattern of passing a NULL into a function to get
> > > > configuration data, and then calling that function again.  This function
> > > > wants to be named...
> > > > 
> > > > ct3_build_cdat_entries_for_mr_or_get_table_size_if_cdat_is_null(...)
> > > > 
> > > > to accurately describe what it does.  Just kinda feels like an extra
> > > > function call for no reason.
> > > > 
> > > > But either way, it works, this is just a nitpick on my side.
> > > >     
> > > > > +static int ct3_build_cdat_table(CDATSubHeader ***cdat_table, void *priv)
> > > > > +{
> > > > > +    g_autofree CDATSubHeader **table = NULL;
> > > > > +    CXLType3Dev *ct3d = priv;
> > > > > +    MemoryRegion *volatile_mr;
> > > > > +    /* ... snip ... */
> > > > > +}    
> > > > 
> > > > s/volatile/nonvolatile    
> > >   
> >