RE: [PATCH v17 3/3] vfio/nvgrace-gpu: Add vfio pci variant module for grace hopper
From: Tian, Kevin
Date: Thu Feb 08 2024 - 02:21:54 EST
> 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();