linux-kernel - [RFC PATCH 3/3] selftests/rseq: Implement rseq tg_vcpu

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Message-Id: <20220201192540.10439-3-mathieu.desnoyers@efficios.com>
Date:   Tue,  1 Feb 2022 14:25:40 -0500
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        "H . Peter Anvin" <hpa@...or.com>, Paul Turner <pjt@...gle.com>,
        linux-api@...r.kernel.org,
        Christian Brauner <christian.brauner@...ntu.com>,
        Florian Weimer <fw@...eb.enyo.de>, David.Laight@...LAB.COM,
        carlos@...hat.com, Peter Oskolkov <posk@...k.io>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [RFC PATCH 3/3] selftests/rseq: Implement rseq tg_vcpu_id field support

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
---
 tools/testing/selftests/rseq/rseq-abi.h | 15 +++++++++++++++
 tools/testing/selftests/rseq/rseq.c     |  6 +++---
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/rseq/rseq-abi.h b/tools/testing/selftests/rseq/rseq-abi.h
index 850827e8d089..929183c2b3c0 100644
--- a/tools/testing/selftests/rseq/rseq-abi.h
+++ b/tools/testing/selftests/rseq/rseq-abi.h
@@ -169,6 +169,21 @@ struct rseq_abi {
 	 * rseq_len. Use the offset immediately after the node_id field as
 	 * rseq_len.
 	 */
+
+	/*
+	 * Restartable sequences tg_vcpu_id field. Updated by the kernel. Read by
+	 * user-space with single-copy atomicity semantics. This field should
+	 * only be read by the thread which registered this data structure.
+	 * Aligned on 32-bit. Contains the current thread's virtual CPU ID
+	 * (allocated uniquely within thread group).
+	 */
+	__u32 tg_vcpu_id;
+
+	/*
+	 * This is a valid end of rseq ABI for the purpose of rseq registration
+	 * rseq_len. Use the offset immediately after the tg_vcpu_id field as
+	 * rseq_len.
+	 */
 } __attribute__((aligned(4 * sizeof(__u64))));
 
 #endif /* _RSEQ_ABI_H */
diff --git a/tools/testing/selftests/rseq/rseq.c b/tools/testing/selftests/rseq/rseq.c
index 4b0e68051db8..c8d30e770d59 100644
--- a/tools/testing/selftests/rseq/rseq.c
+++ b/tools/testing/selftests/rseq/rseq.c
@@ -88,7 +88,7 @@ int rseq_register_current_thread(void)
 		/* Treat libc's ownership as a successful registration. */
 		return 0;
 	}
-	rc = sys_rseq(&__rseq_abi, rseq_offsetofend(struct rseq_abi, node_id), 0, RSEQ_SIG);
+	rc = sys_rseq(&__rseq_abi, rseq_offsetofend(struct rseq_abi, tg_vcpu_id), 0, RSEQ_SIG);
 	if (rc)
 		return -1;
 	assert(rseq_current_cpu_raw() >= 0);
@@ -103,7 +103,7 @@ int rseq_unregister_current_thread(void)
 		/* Treat libc's ownership as a successful unregistration. */
 		return 0;
 	}
-	rc = sys_rseq(&__rseq_abi, rseq_offsetofend(struct rseq_abi, node_id), RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SIG);
+	rc = sys_rseq(&__rseq_abi, rseq_offsetofend(struct rseq_abi, tg_vcpu_id), RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SIG);
 	if (rc)
 		return -1;
 	return 0;
@@ -126,7 +126,7 @@ void rseq_init(void)
 		return;
 	rseq_ownership = 1;
 	rseq_offset = (void *)&__rseq_abi - rseq_thread_pointer();
-	rseq_size = rseq_offsetofend(struct rseq_abi, node_id);
+	rseq_size = rseq_offsetofend(struct rseq_abi, tg_vcpu_id);
 	rseq_flags = 0;
 }
 
-- 
2.17.1