On Fri, Jun 22, 2018 at 11:56 AM, Jakub Kicinski <jakub.kicin...@netronome.com> wrote: > Stopping offload completely if replace of program failed dates > back to days of transparent offload. Back then we wanted to > silently fall back to the in-driver processing. Today we mark > programs for offload when they are loaded into the kernel, so > the transparent offload is no longer a reality. > > Flags check in the driver will only allow replace of a driver > program with another driver program or an offload program with > another offload program. > > When driver program is replaced stopping offload is a no-op, > because driver program isn't offloaded. When replacing > offloaded program if the offload fails the entire operation > will fail all the way back to user space and we should continue > using the old program. IOW when replacing a driver program > stopping offload is unnecessary and when replacing offloaded > program - it's a bug, old program should continue to run. > > In practice this bug would mean that if offload operation was to > fail (either due to FW communication error, kernel OOM or new > program being offloaded but for a different netdev) driver > would continue reporting that previous XDP program is offloaded > but in fact no program will be loaded in hardware. The failure > is fairly unlikely (found by inspection, when working on the code) > but it's unpleasant. > > Backport note: even though the bug was introduced in commit > cafa92ac2553 ("nfp: bpf: add support for XDP_FLAGS_HW_MODE"), > this fix depends on commit 441a33031fe5 ("net: xdp: don't allow > device-bound programs in driver mode"), so this fix is sufficient > only in v4.15 or newer. Kernels v4.13.x and v4.14.x do need to > stop offload if it was transparent/opportunistic, i.e. if > XDP_FLAGS_HW_MODE was not set on running program. > > Fixes: cafa92ac2553 ("nfp: bpf: add support for XDP_FLAGS_HW_MODE") > Signed-off-by: Jakub Kicinski <jakub.kicin...@netronome.com> > Reviewed-by: Quentin Monnet <quentin.mon...@netronome.com>
Acked-by: Song Liu <songliubrav...@fb.com> > --- > drivers/net/ethernet/netronome/nfp/bpf/main.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/ethernet/netronome/nfp/bpf/main.c > b/drivers/net/ethernet/netronome/nfp/bpf/main.c > index fcdfb8e7fdea..7184af94aa53 100644 > --- a/drivers/net/ethernet/netronome/nfp/bpf/main.c > +++ b/drivers/net/ethernet/netronome/nfp/bpf/main.c > @@ -81,10 +81,10 @@ nfp_bpf_xdp_offload(struct nfp_app *app, struct nfp_net > *nn, > > ret = nfp_net_bpf_offload(nn, prog, running, extack); > /* Stop offload if replace not possible */ > - if (ret && prog) > - nfp_bpf_xdp_offload(app, nn, NULL, extack); > + if (ret) > + return ret; > > - nn->dp.bpf_offload_xdp = prog && !ret; > + nn->dp.bpf_offload_xdp = !!prog; > return ret; > } > > -- > 2.17.1 >