linux-kernel - [PATCH bpf-next v1 12/22] rqspinlock: Add basic support for CONFIG

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250107140004.2732830-13-memxor@gmail.com>
Date: Tue,  7 Jan 2025 05:59:54 -0800
From: Kumar Kartikeya Dwivedi <memxor@...il.com>
To: bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Waiman Long <llong@...hat.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Martin KaFai Lau <martin.lau@...nel.org>,
	Eduard Zingerman <eddyz87@...il.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Tejun Heo <tj@...nel.org>,
	Barret Rhoden <brho@...gle.com>,
	Josh Don <joshdon@...gle.com>,
	Dohyun Kim <dohyunkim@...gle.com>,
	kernel-team@...a.com
Subject: [PATCH bpf-next v1 12/22] rqspinlock: Add basic support for CONFIG_PARAVIRT

We ripped out PV and virtualization related bits from rqspinlock in an
earlier commit, however, a fair lock performs poorly within a virtual
machine when the lock holder is preempted. As such, retain the
virt_spin_lock fallback to test and set lock, but with timeout and
deadlock detection.

We don't integrate support for CONFIG_PARAVIRT_SPINLOCKS yet, as that
requires more involved algorithmic changes and introduces more
complexity. It can be done when the need arises in the future.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@...il.com>
---
 arch/x86/include/asm/rqspinlock.h | 20 ++++++++++++++++
 include/asm-generic/rqspinlock.h  |  7 ++++++
 kernel/locking/rqspinlock.c       | 38 +++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+)
 create mode 100644 arch/x86/include/asm/rqspinlock.h

diff --git a/arch/x86/include/asm/rqspinlock.h b/arch/x86/include/asm/rqspinlock.h
new file mode 100644
index 000000000000..ecfb7dfe6370
--- /dev/null
+++ b/arch/x86/include/asm/rqspinlock.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_RQSPINLOCK_H
+#define _ASM_X86_RQSPINLOCK_H
+
+#include <asm/paravirt.h>
+
+#ifdef CONFIG_PARAVIRT
+DECLARE_STATIC_KEY_FALSE(virt_spin_lock_key);
+
+#define resilient_virt_spin_lock_enabled resilient_virt_spin_lock_enabled
+static __always_inline bool resilient_virt_spin_lock_enabled(void)
+{
+       return static_branch_likely(&virt_spin_lock_key);
+}
+
+#endif /* CONFIG_PARAVIRT */
+
+#include <asm-generic/rqspinlock.h>
+
+#endif /* _ASM_X86_RQSPINLOCK_H */
diff --git a/include/asm-generic/rqspinlock.h b/include/asm-generic/rqspinlock.h
index c7e33ccc57a6..dc436ab01471 100644
--- a/include/asm-generic/rqspinlock.h
+++ b/include/asm-generic/rqspinlock.h
@@ -17,6 +17,13 @@ struct qspinlock;
 
 extern int resilient_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val, u64 timeout);
 
+#ifndef resilient_virt_spin_lock_enabled
+static __always_inline bool resilient_virt_spin_lock_enabled(void)
+{
+	return false;
+}
+#endif
+
 /*
  * Default timeout for waiting loops is 0.5 seconds
  */
diff --git a/kernel/locking/rqspinlock.c b/kernel/locking/rqspinlock.c
index b7c86127d288..e397f91ebcf6 100644
--- a/kernel/locking/rqspinlock.c
+++ b/kernel/locking/rqspinlock.c
@@ -247,6 +247,41 @@ static noinline int check_timeout(struct qspinlock *lock, u32 mask,
  */
 #define RES_RESET_TIMEOUT(ts) ({ (ts).timeout_end = 0; })
 
+#ifdef CONFIG_PARAVIRT
+
+static inline int resilient_virt_spin_lock(struct qspinlock *lock, struct rqspinlock_timeout *ts)
+{
+	int val, ret = 0;
+
+	RES_RESET_TIMEOUT(*ts);
+	grab_held_lock_entry(lock);
+retry:
+	val = atomic_read(&lock->val);
+
+	if (val || !atomic_try_cmpxchg(&lock->val, &val, _Q_LOCKED_VAL)) {
+		if (RES_CHECK_TIMEOUT(*ts, ret, ~0u)) {
+			lockevent_inc(rqspinlock_lock_timeout);
+			goto timeout;
+		}
+		cpu_relax();
+		goto retry;
+	}
+
+	return 0;
+timeout:
+	release_held_lock_entry();
+	return ret;
+}
+
+#else
+
+static __always_inline int resilient_virt_spin_lock(struct qspinlock *lock, struct rqspinlock_timeout *ts)
+{
+	return 0;
+}
+
+#endif /* CONFIG_PARAVIRT */
+
 /*
  * Per-CPU queue node structures; we can never have more than 4 nested
  * contexts: task, softirq, hardirq, nmi.
@@ -287,6 +322,9 @@ int __lockfunc resilient_queued_spin_lock_slowpath(struct qspinlock *lock, u32 v
 
 	RES_INIT_TIMEOUT(ts, timeout);
 
+	if (resilient_virt_spin_lock_enabled())
+		return resilient_virt_spin_lock(lock, &ts);
+
 	/*
 	 * Wait for in-progress pending->locked hand-overs with a bounded
 	 * number of spins so that we guarantee forward progress.
-- 
2.43.5