RE: [PATCH v17 3/3] vfio/nvgrace-gpu: Add vfio pci variant module for grace hopper

[Tian, Kevin]

> From: Ankit Agrawal <ankita@xxxxxxxxxx>
> Sent: Thursday, February 8, 2024 3:13 PM
> >> > +    * Determine how many bytes to be actually read from the
> >> > device memory.
> >> > +    * Read request beyond the actual device memory size is
> >> > filled with ~0,
> >> > +    * while those beyond the actual reported size is skipped.
> >> > +    */
> >> > +   if (offset >= memregion->memlength)
> >> > +           mem_count = 0;
> >>
> >> If mem_count == 0, going through nvgrace_gpu_map_and_read() is not
> >> necessary.
> >
> > Harmless, other than the possibly unnecessary call through to
> > nvgrace_gpu_map_device_mem().  Maybe both
> nvgrace_gpu_map_and_read()
> > and nvgrace_gpu_map_and_write() could conditionally return 0 as their
> > first operation when !mem_count.  Thanks,
> >
> >Alex
> 
> IMO, this seems like adding too much code to reduce the call length for a
> very specific case. If there aren't any strong opinion on this, I'm planning to
> leave this code as it is.

a slight difference. if mem_count==0 the result should always succeed
no matter nvgrace_gpu_map_device_mem() succeeds or not. Of course
if it fails it's already a big problem probably nobody cares about the subtle
difference when reading non-exist range.

but regarding to readability it's still clearer:

if (mem_count)
	nvgrace_gpu_map_and_read();