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Date: Mon, 16 Mar 2026 16:31:31 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>
Cc: netdev@vger.kernel.org, Michael Chan <michael.chan@broadcom.com>, Pavan
 Chebbi <pavan.chebbi@broadcom.com>, Andrew Lunn <andrew+netdev@lunn.ch>,
 "David S. Miller" <davem@davemloft.net>, Eric Dumazet
 <edumazet@google.com>, Paolo Abeni <pabeni@redhat.com>, Simon Horman
 <horms@kernel.org>, linux-kselftest@vger.kernel.org, Willem de Bruijn
 <willemb@google.com>, Shuah Khan <shuah@kernel.org>, Maxime Chevallier
 <maxime.chevallier@bootlin.com>, Andrew Lunn <andrew@lunn.ch>,
 intel-wired-lan@lists.osuosl.org, Przemek Kitszel
 <przemyslaw.kitszel@intel.com>
Subject: Re: [PATCH net-next v4 0/3] ethtool: Dynamic RSS context
 indirection table resizing
Message-ID: <20260316163131.2ff161c5@kernel.org>
In-Reply-To: <87a4w9p95i.fsf@all.your.base.are.belong.to.us>
References: <20260313071322.3489243-1-bjorn@kernel.org>
	<20260314093518.43b820b7@kernel.org>
	<87a4w9p95i.fsf@all.your.base.are.belong.to.us>
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On Sun, 15 Mar 2026 13:30:33 +0100 Bj=C3=B6rn T=C3=B6pel wrote:
> Jakub Kicinski <kuba@kernel.org> writes:
>=20
> > On Fri, 13 Mar 2026 08:13:12 +0100 Bj=C3=B6rn T=C3=B6pel wrote: =20
> >> Some NICs (e.g. bnxt) change their RSS indirection table size based on
> >> the queue count, because the hardware table is a shared resource. The
> >> ethtool core locks ctx->indir_size at context creation, so drivers
> >> have to reject channel changes when RSS contexts exist.
> >>=20
> >> This series adds resize helpers and wires them up in bnxt. =20
> >
> > Sorry Bjorn, I was typing the explanation below and I realized that=20
> > we may be violating user intent. We should already record the user_size
> > from rss_set_prep_indir() as part of the context (and presumably some
> > netdev state for the main context?) and don't allow shrinking the
> > context below that mark.. =20
>=20
> Don't be sorry! Good catch, and glad you caught it now rather than after
> it landed.
>=20
> I'll respin with user_size tracked in the context (and netdev state for
> context 0) as a lower bound, so resize never folds below the size the
> user explicitly configured.
>=20
> WDYT?

Yes, keep in mind that AFAIR context 0 is not currently tracked
in the xarray. So maybe add the size of the main / default context=20
as a field in struct ethtool_netdev_state ?  Or we can start tracking
it (partially). IDK what's cleaner.