linux-kernel - Re: [net-next,v4,01/13] octeontx2-af: npc: cn20k: Index management

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Message-ID: <aW2sc2JAxGJGe88W@rkannoth-OptiPlex-7090>
Date: Mon, 19 Jan 2026 09:30:51 +0530
From: Ratheesh Kannoth <rkannoth@...vell.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>
Subject: Re: [net-next,v4,01/13] octeontx2-af: npc: cn20k: Index management

On 2026-01-18 at 06:10:17, Jakub Kicinski (kuba@...nel.org) wrote:
> This is an AI-generated review of your patch. The human sending this
> email has considered the AI review valid, or at least plausible.
>
> For local reproduction steps see https://netdev-ai.bots.linux.dev/ai-local.html
> ---
> octeontx2-af: npc: cn20k: Index management
>
> This patch adds MCAM index management for CN20K silicon, implementing
> contiguous and non-contiguous allocation schemes with reference, limit,
> and priority parameters across the new subbank architecture.
>
> > diff --git a/drivers/net/ethernet/marvell/octeontx2/af/cn20k/npc.c b/drivers/net/ethernet/marvell/octeontx2/af/cn20k/npc.c
> > new file mode 100644
> > index 000000000000..ebccc780ab8e
> > --- /dev/null
> > +++ b/drivers/net/ethernet/marvell/octeontx2/af/cn20k/npc.c
>
> [ ... ]
>
> > +static int npc_idx_free(struct rvu *rvu, u16 *mcam_idx, int count,
> > +			bool maps_del)
> > +{
> > +	struct npc_subbank *sb;
> > +	int idx, i;
> > +	bool ret;
> > +	int rc;
> > +
> > +	for (i = 0; i < count; i++) {
> > +		rc =  npc_mcam_idx_2_subbank_idx(rvu, mcam_idx[i],
> > +						 &sb, &idx);
> > +		if (rc)
> > +			return rc;
> > +
> > +		ret = npc_subbank_free(rvu, sb, idx);
> > +		if (ret)
> > +			return -EINVAL;
>
> If an error occurs partway through this loop, for example when freeing
> entry i out of count entries, entries from i+1 to count-1 remain allocated
> but are never freed. Could this leak MCAM slots when npc_idx_free() is
> called from error paths in npc_multi_subbank_ref_alloc() or
> npc_subbank_noref_alloc()?
if npc_idx_free() failed for an allocated index, system wont be able to function
properly as index management goes for a toss. So there is no point in rolling back.
i moved npc_mcam_idx_2_subbank_idx() out of the loop and checked whether all indexes can
be converted to proper mcam index.
>
> > +
> > +		if (!maps_del)
> > +			continue;
> > +
> > +		rc = npc_del_from_pf_maps(rvu, mcam_idx[i]);
> > +		if (rc)
> > +			return rc;
> > +	}
> > +
> > +	return 0;
> > +}
>
> [ ... ]
>
> > +static int npc_priv_init(struct rvu *rvu)
> > +{
>
> [ ... ]
>
> > +	npc_priv.sb = kcalloc(num_subbanks, sizeof(struct npc_subbank),
> > +			      GFP_KERNEL);
> > +	if (!npc_priv.sb)
> > +		return -ENOMEM;
> > +
> > +	xa_init_flags(&npc_priv.xa_sb_used, XA_FLAGS_ALLOC);
> > +	xa_init_flags(&npc_priv.xa_sb_free, XA_FLAGS_ALLOC);
> > +	xa_init_flags(&npc_priv.xa_idx2pf_map, XA_FLAGS_ALLOC);
> > +	xa_init_flags(&npc_priv.xa_pf_map, XA_FLAGS_ALLOC);
> > +
> > +	if (npc_create_srch_order(num_subbanks)) {
> > +		kfree(npc_priv.sb);
> > +		return -ENOMEM;
> > +	}
>
> The four xarrays initialized above are not destroyed before returning
> here. Should xa_destroy() be called for xa_sb_used, xa_sb_free,
> xa_idx2pf_map, and xa_pf_map on this error path?
ACK.
>
> [ ... ]
>
> > +	npc_priv.xa_pf2idx_map = kcalloc(npc_priv.pf_cnt,
> > +					 sizeof(struct xarray),
> > +					 GFP_KERNEL);
> > +	if (!npc_priv.xa_pf2idx_map) {
> > +		kfree(subbank_srch_order);
> > +		kfree(npc_priv.sb);
> > +		return -ENOMEM;
> > +	}
>
> Same question here - the four xarrays are still not destroyed on this
> error path.
ACK.
>
> > +
> > +	for (i = 0; i < npc_priv.pf_cnt; i++)
> > +		xa_init_flags(&npc_priv.xa_pf2idx_map[i], XA_FLAGS_ALLOC);
> > +
> > +	return 0;
> > +}
> --
> pw-bot: cr