linux-kernel - Re: [EXTERNAL] Re: [PATCH net-next v4 2/6] net: ti: icssg-prueth: Add XSK pool helpers

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Message-ID: <20251104154828.7aa20642@kernel.org>
Date: Tue, 4 Nov 2025 15:48:28 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Meghana Malladi <m-malladi@...com>
Cc: Paolo Abeni <pabeni@...hat.com>, <horms@...nel.org>,
 <namcao@...utronix.de>, <vadim.fedorenko@...ux.dev>,
 <jacob.e.keller@...el.com>, <christian.koenig@....com>,
 <sumit.semwal@...aro.org>, <sdf@...ichev.me>, <john.fastabend@...il.com>,
 <hawk@...nel.org>, <daniel@...earbox.net>, <ast@...nel.org>,
 <edumazet@...gle.com>, <davem@...emloft.net>, <andrew+netdev@...n.ch>,
 <linaro-mm-sig@...ts.linaro.org>, <dri-devel@...ts.freedesktop.org>,
 <linux-media@...r.kernel.org>, <bpf@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
 <linux-arm-kernel@...ts.infradead.org>, <srk@...com>, Vignesh Raghavendra
 <vigneshr@...com>, Roger Quadros <rogerq@...nel.org>, <danishanwar@...com>
Subject: Re: [EXTERNAL] Re: [PATCH net-next v4 2/6] net: ti: icssg-prueth:
 Add XSK pool helpers

On Tue, 4 Nov 2025 14:23:24 +0530 Meghana Malladi wrote:
> > I tried honoring Jakub's comment to avoid freeing the rx memory wherever 
> > necessary.
> > 
> > "In case of icssg driver, freeing the rx memory is necessary as the
> > rx descriptor memory is owned by the cppi dma controller and can be
> > mapped to a single memory model (pages/xdp buffers) at a given time.
> > In order to remap it, the memory needs to be freed and reallocated."
> 
> Just to make sure we are on the same page, does the above explanation 
> make sense to you or do you want me to make any changes in this series 
> for v5 ?

No. Based on your reply below you seem to understand what is being
asked, so you're expected to do it.

> >> I think you should:
> >> - stop the H/W from processing incoming packets,
> >> - spool all the pending packets
> >> - attach/detach the xsk_pool
> >> - refill the ring
> >> - re-enable the H/W
> > 
> > Current implementation follows the same sequence:
> > 1. Does a channel teardown -> stop incoming traffic
> > 2. free the rx descriptors from free queue and completion queue -> spool 
> > all pending packets/descriptors
> > 3. attach/detach the xsk pool
> > 4. allocate rx descriptors and fill the freeq after mapping them to the 
> > correct memory buffers -> refill the ring
> > 5. restart the NAPI - re-enable the H/W to recv the traffic
> > 
> > I am still working on skipping 2 and 4 steps but this will be a long 
> > shot. Need to make sure all corner cases are getting covered. If this 
> > approach looks doable without causing any regressions I might post it as 
> > a followup patch later in the future.