linux-kernel - [PATCH RFC iwl-next 01/12] libeth: add cacheline / struct alignment helpers

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Message-ID: <20240510152620.2227312-2-aleksander.lobakin@intel.com>
Date: Fri, 10 May 2024 17:26:09 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: intel-wired-lan@...ts.osuosl.org
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>,
	Tony Nguyen <anthony.l.nguyen@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	nex.sw.ncis.osdt.itp.upstreaming@...el.com,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH RFC iwl-next 01/12] libeth: add cacheline / struct alignment helpers

Following the latest netdev trend, i.e. effective and usage-based field
cacheline placement, add helpers to group and then assert struct fields
by cachelines.
For 64-bit with 64-byte cachelines, the assertions are more strict as
the size can then be easily predicted. For the rest, just make sure
they don't cross the specified bound.

Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>
---
 include/net/libeth/cache.h | 64 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 include/net/libeth/cache.h

diff --git a/include/net/libeth/cache.h b/include/net/libeth/cache.h
new file mode 100644
index 000000000000..3245a20b22d3
--- /dev/null
+++ b/include/net/libeth/cache.h
@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright (C) 2024 Intel Corporation */
+
+#ifndef __LIBETH_CACHE_H
+#define __LIBETH_CACHE_H
+
+#include <linux/cache.h>
+
+/* __aligned_largest is architecture-dependent. Get the actual alignment */
+#define ___LIBETH_LARGEST_ALIGN						   \
+	sizeof(struct { long __UNIQUE_ID(long_); } __aligned_largest)
+#define __LIBETH_LARGEST_ALIGN						   \
+	(___LIBETH_LARGEST_ALIGN > SMP_CACHE_BYTES ?			   \
+	 ___LIBETH_LARGEST_ALIGN : SMP_CACHE_BYTES)
+#define __LIBETH_LARGEST_ALIGNED(sz)					   \
+	ALIGN(sz, __LIBETH_LARGEST_ALIGN)
+
+#define __libeth_cacheline_group_begin(grp)				   \
+	__cacheline_group_begin(grp) __aligned(__LIBETH_LARGEST_ALIGN)
+#define __libeth_cacheline_group_end(grp)				   \
+	__cacheline_group_end(grp) __aligned(4)
+
+#define libeth_cacheline_group(grp, ...)				   \
+	struct_group(grp,						   \
+		__libeth_cacheline_group_begin(grp);			   \
+		__VA_ARGS__						   \
+		__libeth_cacheline_group_end(grp);			   \
+	)
+
+#if defined(CONFIG_64BIT) && L1_CACHE_BYTES == 64
+#define libeth_cacheline_group_assert(type, grp, sz)			   \
+	static_assert(offsetof(type, __cacheline_group_end__##grp) -	   \
+		      offsetofend(type, __cacheline_group_begin__##grp) == \
+		      (sz))
+#define __libeth_cacheline_struct_assert(type, sz)			   \
+	static_assert(sizeof(type) == (sz))
+#else /* !CONFIG_64BIT || L1_CACHE_BYTES != 64 */
+#define libeth_cacheline_group_assert(type, grp, sz)			   \
+	static_assert(offsetof(type, __cacheline_group_end__##grp) -	   \
+		      offsetofend(type, __cacheline_group_begin__##grp) <= \
+		      (sz))
+#define __libeth_cacheline_struct_assert(type, sz)			   \
+	static_assert(sizeof(type) <= (sz))
+#endif /* !CONFIG_64BIT || L1_CACHE_BYTES != 64 */
+
+#define __libeth_cls1(sz1)						   \
+	__LIBETH_LARGEST_ALIGNED(sz1)
+#define __libeth_cls2(sz1, sz2)						   \
+	(__LIBETH_LARGEST_ALIGNED(sz1) + __LIBETH_LARGEST_ALIGNED(sz2))
+#define __libeth_cls3(sz1, sz2, sz3)					   \
+	(__LIBETH_LARGEST_ALIGNED(sz1) + __LIBETH_LARGEST_ALIGNED(sz2) +   \
+	 __LIBETH_LARGEST_ALIGNED(sz3))
+#define __libeth_cls(...)						   \
+	CONCATENATE(__libeth_cls, COUNT_ARGS(__VA_ARGS__))(__VA_ARGS__)
+#define libeth_cacheline_struct_assert(type, ...)			   \
+	__libeth_cacheline_struct_assert(type, __libeth_cls(__VA_ARGS__))
+
+#define libeth_cacheline_set_assert(type, ro, rw, c)			   \
+	libeth_cacheline_group_assert(type, read_mostly, ro);		   \
+	libeth_cacheline_group_assert(type, read_write, rw);		   \
+	libeth_cacheline_group_assert(type, cold, c);			   \
+	libeth_cacheline_struct_assert(type, ro, rw, c)
+
+#endif /* __LIBETH_CACHE_H */
-- 
2.45.0