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ACLs in Spectrum-2 and newer ASICs can reside in the algorithmic TCAM
(A-TCAM) or in the ordinary circuit TCAM (C-TCAM). The former can
contain more ACLs (i.e., tc filters), but the number of masks in each
region (i.e., tc chain) is limited.
In order to mitigate the effects of the above limitation, the device
allows filters to share a single mask if their masks only differ in up
to 8 consecutive bits. For example, dst_ip/25 can be represented using
dst_ip/24 with a delta of 1 bit. The C-TCAM does not have a limit on the
number of masks being used (and therefore does not support mask
aggregation), but can contain a limited number of filters.
The driver uses the "objagg" library to perform the mask aggregation by
passing it objects that consist of the filter's mask and whether the
filter is to be inserted into the A-TCAM or the C-TCAM since filters in
different TCAMs cannot share a mask.
The set of created objects is dependent on the insertion order of the
filters and is not necessarily optimal. Therefore, the driver will
periodically ask the library to compute a more optimal set ("hints") by
looking at all the existing objects.
When the library asks the driver whether two objects can be aggregated
the driver only compares the provided masks and ignores the A-TCAM /
C-TCAM indication. This is the right thing to do since the goal is to
move as many filters as possible to the A-TCAM. The driver also forbids
two identical masks from being aggregated since this can only happen if
one was intentionally put in the C-TCAM to avoid a conflict in the
A-TCAM.
The above can result in the following set of hints:
H1: {mask X, A-TCAM} -> H2: {mask Y, A-TCAM} // X is Y + delta
H3: {mask Y, C-TCAM} -> H4: {mask Z, A-TCAM} // Y is Z + delta
After getting the hints from the library the driver will start migrating
filters from one region to another while consulting the computed hints
and instructing the device to perform a lookup in both regions during
the transition.
Assuming a filter with mask X is being migrated into the A-TCAM in the
new region, the hints lookup will return H1. Since H2 is the parent of
H1, the library will try to find the object associated with it and
create it if necessary in which case another hints lookup (recursive)
will be performed. This hints lookup for {mask Y, A-TCAM} will either
return H2 or H3 since the driver passes the library an object comparison
function that ignores the A-TCAM / C-TCAM indication.
This can eventually lead to nested objects which are not supported by
the library [1].
Fix by removing the object comparison function from both the driver and
the library as the driver was the only user. That way the lookup will
only return exact matches.
I do not have a reliable reproducer that can reproduce the issue in a
timely manner, but before the fix the issue would reproduce in several
minutes and with the fix it does not reproduce in over an hour.
Note that the current usefulness of the hints is limited because they
include the C-TCAM indication and represent aggregation that cannot
actually happen. This will be addressed in net-next.
[1]
WARNING: CPU: 0 PID: 153 at lib/objagg.c:170 objagg_obj_parent_assign+0xb5/0xd0
Modules linked in:
CPU: 0 PID: 153 Comm: kworker/0:18 Not tainted 6.9.0-rc6-custom-g70fbc2c1c38b #42
Hardware name: Mellanox Technologies Ltd. MSN3700C/VMOD0008, BIOS 5.11 10/10/2018
Workqueue: mlxsw_core mlxsw_sp_acl_tcam_vregion_rehash_work
RIP: 0010:objagg_obj_parent_assign+0xb5/0xd0
[...]
Call Trace:
<TASK>
__objagg_obj_get+0x2bb/0x580
objagg_obj_get+0xe/0x80
mlxsw_sp_acl_erp_mask_get+0xb5/0xf0
mlxsw_sp_acl_atcam_entry_add+0xe8/0x3c0
mlxsw_sp_acl_tcam_entry_create+0x5e/0xa0
mlxsw_sp_acl_tcam_vchunk_migrate_one+0x16b/0x270
mlxsw_sp_acl_tcam_vregion_rehash_work+0xbe/0x510
process_one_work+0x151/0x370
Fixes: 9069a3817d82 ("lib: objagg: implement optimization hints assembly and use hints for object creation")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Amit Cohen <amcohen@nvidia.com>
Tested-by: Alexander Zubkov <green@qrator.net>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
63 lines
1.9 KiB
C
63 lines
1.9 KiB
C
/* SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0 */
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/* Copyright (c) 2018 Mellanox Technologies. All rights reserved */
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#ifndef _OBJAGG_H
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#define _OBJAGG_H
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struct objagg_ops {
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size_t obj_size;
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bool (*delta_check)(void *priv, const void *parent_obj,
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const void *obj);
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void * (*delta_create)(void *priv, void *parent_obj, void *obj);
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void (*delta_destroy)(void *priv, void *delta_priv);
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void * (*root_create)(void *priv, void *obj, unsigned int root_id);
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#define OBJAGG_OBJ_ROOT_ID_INVALID UINT_MAX
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void (*root_destroy)(void *priv, void *root_priv);
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};
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struct objagg;
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struct objagg_obj;
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struct objagg_hints;
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const void *objagg_obj_root_priv(const struct objagg_obj *objagg_obj);
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const void *objagg_obj_delta_priv(const struct objagg_obj *objagg_obj);
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const void *objagg_obj_raw(const struct objagg_obj *objagg_obj);
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struct objagg_obj *objagg_obj_get(struct objagg *objagg, void *obj);
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void objagg_obj_put(struct objagg *objagg, struct objagg_obj *objagg_obj);
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struct objagg *objagg_create(const struct objagg_ops *ops,
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struct objagg_hints *hints, void *priv);
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void objagg_destroy(struct objagg *objagg);
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struct objagg_obj_stats {
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unsigned int user_count;
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unsigned int delta_user_count; /* includes delta object users */
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};
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struct objagg_obj_stats_info {
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struct objagg_obj_stats stats;
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struct objagg_obj *objagg_obj; /* associated object */
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bool is_root;
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};
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struct objagg_stats {
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unsigned int root_count;
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unsigned int stats_info_count;
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struct objagg_obj_stats_info stats_info[];
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};
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const struct objagg_stats *objagg_stats_get(struct objagg *objagg);
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void objagg_stats_put(const struct objagg_stats *objagg_stats);
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enum objagg_opt_algo_type {
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OBJAGG_OPT_ALGO_SIMPLE_GREEDY,
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};
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struct objagg_hints *objagg_hints_get(struct objagg *objagg,
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enum objagg_opt_algo_type opt_algo_type);
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void objagg_hints_put(struct objagg_hints *objagg_hints);
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const struct objagg_stats *
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objagg_hints_stats_get(struct objagg_hints *objagg_hints);
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#endif
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