Re: [dpdk-dev] [PATCH] gpudev: introduce memory API

[Thomas Monjalon <thomas@monjalon.net>]

03/06/2021 09:49, Andrew Rybchenko:
> On 6/3/21 10:26 AM, Thomas Monjalon wrote:
> > 03/06/2021 09:06, Andrew Rybchenko:
> >> On 6/2/21 11:35 PM, Thomas Monjalon wrote:
> >>> + * Allocate a chunk of memory on the GPU.
> >>
> >> Looking a below function it is required to clarify here if
> >> the memory is visible or invisible to GPU (or both allowed).
> > 
> > This function allocates on the GPU so it is visible by the GPU.
> > I feel I misunderstand your question.
> 
> Below function says rte_gpu_malloc_visible() and its
> description highlights that allocated memory is visible to GPU.
> My problem that I don't understand what's the difference
> between these two functions.

One function allocates in GPU mem, the other allows the GPU to use CPU mem.

> >>> + */
> >>> +__rte_experimental
> >>> +int rte_gpu_malloc(uint16_t gpu_id, size_t size, void **ptr);
> >>
> >> May be *malloc() should return a pointer and "negative"
> >> values used to report various errnos?
> > 
> > I don't understand what you mean by negative values if it is a pointer.
> > We could return a pointer and use rte_errno.
> 
> I was talking about something like (void *)(-ENOMEM), but it is
> a bad idea. NULL + rte_errno is much better.
> 
> However, may be I'd kept callback as is set rte_error in lib if
> negative value is returned by the callback. This way we'll be
> safe against lost rte_errno update in drivers.

OK