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Some modern cpus disable X86_FEATURE_RETPOLINE feature,
even if a direct call can still be beneficial.
Even when IBRS is present, an indirect call is more expensive
than a direct one:
Direct Calls:
Compilers can perform powerful optimizations like inlining,
where the function body is directly inserted at the call site,
eliminating call overhead entirely.
Indirect Calls:
Inlining is much harder, if not impossible, because the compiler
doesn't know the target function at compile time.
Techniques like Indirect Call Promotion can help by using
profile-guided optimization to turn frequently taken indirect calls
into conditional direct calls, but they still add complexity
and potential overhead compared to a truly direct call.
In this patch, I split tc_skip_wrapper in two different
static keys, one for tc_act() (tc_skip_wrapper_act)
and one for tc_classify() (tc_skip_wrapper_cls).
Then I enable the tc_skip_wrapper_cls only if the count
of builtin classifiers is above one.
I enable tc_skip_wrapper_act only it the count of builtin
actions is above one.
In our production kernels, we only have CONFIG_NET_CLS_BPF=y
and CONFIG_NET_ACT_BPF=y. Other are modules or are not compiled.
Tested on AMD Turin cpus, cls_bpf_classify() cost went
from 1% down to 0.18 %, and FDO will be able to inline
it in tcf_classify() for further gains.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Pedro Tammela <pctammela@mojatatu.com>
Reviewed-by: Victor Nogueira <victor@mojatatu.com>
Link: https://patch.msgid.link/20260307133601.3863071-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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dependent patches
Merge in pending alternatives patching infrastructure changes, before
applying more patches.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Step 5/10 of the namespace unification of CPU mitigations related Kconfig options.
[ mingo: Converted a few more uses in comments/messages as well. ]
Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Ariel Miculas <amiculas@cisco.com>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20231121160740.1249350-6-leitao@debian.org
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The tc ipt action was intended to run all netfilter/iptables target.
Unfortunately it has not benefitted over the years from proper updates when
netfilter changes, and for that reason it has remained rudimentary.
Pinging a bunch of people that i was aware were using this indicates that
removing it wont affect them.
Retire it to reduce maintenance efforts. Buh-bye.
Reviewed-by: Victor Noguiera <victor@mojatatu.com>
Reviewed-by: Pedro Tammela <pctammela@mojatatu.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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The rsvp classifier has served us well for about a quarter of a century but has
has not been getting much maintenance attention due to lack of known users.
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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The tcindex classifier has served us well for about a quarter of a century
but has not been getting much TLC due to lack of known users. Most recently
it has become easy prey to syzkaller. For this reason, we are retiring it.
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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Rudi reports a compilation failure on x86_64 when CONFIG_NET_CLS or
CONFIG_NET_CLS_ACT is not set but CONFIG_RETPOLINE is set.
A misplaced '#endif' was causing the issue.
Fixes: 7f0e810220e2 ("net/sched: add retpoline wrapper for tc")
Tested-by: Rudi Heitbaum <rudi@heitbaum.com>
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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On kernels using retpoline as a spectrev2 mitigation,
optimize actions and filters that are compiled as built-ins into a direct call.
On subsequent patches we expose the classifiers and actions functions
and wire up the wrapper into tc.
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Victor Nogueira <victor@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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