Subject: Re: [PATCH net-next v7 10/12] selftests: ncdevmem: Run selftest when none of the -s or -c has been provided

From: Stanislav Fomichev <[email-masked]>
Date: Mon, 4 Nov 2024 19:31:58 -0800

On 11/04, Joe Damato wrote:
> On Mon, Nov 04, 2024 at 10:14:28AM -0800, Stanislav Fomichev wrote:
> > This will be used as a 'probe' mode in the selftest to check whether
> > the device supports the devmem or not. Use hard-coded queue layout
> > (two last queues) and prevent user from passing custom -q and/or -t.
> > 
> > Reviewed-by: Mina Almasry <[email-masked]>
> > Signed-off-by: Stanislav Fomichev <[email-masked]>
> > ---
> >  tools/testing/selftests/net/ncdevmem.c | 42 ++++++++++++++++++++------
> >  1 file changed, 32 insertions(+), 10 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/net/ncdevmem.c b/tools/testing/selftests/net/ncdevmem.c
> > index 044198ce02a7..270a77206f65 100644
> > --- a/tools/testing/selftests/net/ncdevmem.c
> > +++ b/tools/testing/selftests/net/ncdevmem.c
> > @@ -76,7 +76,7 @@ static char *client_ip;
> >  static char *port;
> >  static size_t do_validation;
> >  static int start_queue = -1;
> > -static int num_queues = 1;
> > +static int num_queues = -1;
> >  static char *ifname;
> >  static unsigned int ifindex;
> >  static unsigned int dmabuf_id;
> > @@ -731,19 +731,31 @@ int main(int argc, char *argv[])
> >  		}
> >  	}
> >  
> > -	if (!server_ip)
> > -		error(1, 0, "Missing -s argument\n");
> > -
> > -	if (!port)
> > -		error(1, 0, "Missing -p argument\n");
> > -
> >  	if (!ifname)
> >  		error(1, 0, "Missing -f argument\n");
> >  
> >  	ifindex = if_nametoindex(ifname);
> >  
> > -	if (start_queue < 0) {
> > -		start_queue = rxq_num(ifindex) - 1;
> > +	if (!server_ip && !client_ip) {
> > +		if (start_queue < 0 && num_queues < 0) {
> > +			num_queues = rxq_num(ifindex);
> > +			if (num_queues < 0)
> > +				error(1, 0, "couldn't detect number of queues\n");
> > +			/* make sure can bind to multiple queues */
> > +			start_queue = num_queues / 2;
> > +			num_queues /= 2;
> 
> Sorry for the beginner question :) -- is it possible that rxq_num
> ever returns 1 and thus start_queue = 0, num_queues = 0
>
> > +		}
> > +
> > +		if (start_queue < 0 || num_queues < 0)
> > +			error(1, 0, "Both -t and -q are required\n");
> 
> And then isn't caught here because this only checks < 0 (instead of
> num_queues <= 0) ?

In theory it's possible to configure a netdev with a single queue. I can
add an extra 'num_queues == 1' check just in case...