From: Eric Dumazet <eric.dumazet@gmail.com>
To: Ingo Molnar <mingo@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E . McKenney" <paulmck@kernel.org>,
Boqun Feng <boqun.feng@gmail.com>,
Arjun Roy <arjunroy@google.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Eric Dumazet <edumazet@google.com>,
Eric Dumazet <eric.dumazet@gmail.com>
Subject: [PATCH v3 3/3] rseq: optimise rseq_get_rseq_cs() and clear_rseq_cs()
Date: Tue, 13 Apr 2021 13:33:52 -0700 [thread overview]
Message-ID: <20210413203352.71350-4-eric.dumazet@gmail.com> (raw)
In-Reply-To: <20210413203352.71350-1-eric.dumazet@gmail.com>
From: Eric Dumazet <edumazet@google.com>
Commit ec9c82e03a74 ("rseq: uapi: Declare rseq_cs field as union,
update includes") added regressions for our servers.
Using copy_from_user() and clear_user() for 64bit values
is suboptimal.
We can use faster put_user() and get_user() on 64bit arches.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Arjun Roy <arjunroy@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
---
kernel/rseq.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/kernel/rseq.c b/kernel/rseq.c
index cfe01ab5253c1c424c0e8b25acbb6a8e1b41a5b6..35f7bd0fced0e2dd8aed819e054dac03f024388a 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -127,8 +127,13 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs)
u32 sig;
int ret;
+#ifdef CONFIG_64BIT
+ if (get_user(ptr, &t->rseq->rseq_cs.ptr64))
+ return -EFAULT;
+#else
if (copy_from_user(&ptr, &t->rseq->rseq_cs.ptr64, sizeof(ptr)))
return -EFAULT;
+#endif
if (!ptr) {
memset(rseq_cs, 0, sizeof(*rseq_cs));
return 0;
@@ -211,9 +216,13 @@ static int clear_rseq_cs(struct task_struct *t)
*
* Set rseq_cs to NULL.
*/
+#ifdef CONFIG_64BIT
+ return put_user(0UL, &t->rseq->rseq_cs.ptr64);
+#else
if (clear_user(&t->rseq->rseq_cs.ptr64, sizeof(t->rseq->rseq_cs.ptr64)))
return -EFAULT;
return 0;
+#endif
}
/*
--
2.31.1.295.g9ea45b61b8-goog
next prev parent reply other threads:[~2021-04-13 20:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-13 20:33 [PATCH v3 0/3] rseq: minor optimizations Eric Dumazet
2021-04-13 20:33 ` [PATCH v3 1/3] rseq: optimize rseq_update_cpu_id() Eric Dumazet
2021-04-15 8:37 ` [tip: sched/core] rseq: Optimize rseq_update_cpu_id() tip-bot2 for Eric Dumazet
2021-04-13 20:33 ` [PATCH v3 2/3] rseq: remove redundant access_ok() Eric Dumazet
2021-04-15 8:37 ` [tip: sched/core] rseq: Remove " tip-bot2 for Eric Dumazet
2021-04-13 20:33 ` Eric Dumazet [this message]
2021-04-15 8:37 ` [tip: sched/core] rseq: Optimise rseq_get_rseq_cs() and clear_rseq_cs() tip-bot2 for Eric Dumazet
2021-04-13 20:40 ` [PATCH v3 0/3] rseq: minor optimizations Mathieu Desnoyers
2021-04-14 7:51 ` Peter Zijlstra
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