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Date: Tue, 28 May 2024 15:48:35 +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>,
Mina Almasry <almasrymina@...gle.com>,
nex.sw.ncis.osdt.itp.upstreaming@...el.com,
netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 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>
---
scripts/kernel-doc | 1 +
include/net/libeth/cache.h | 100 +++++++++++++++++++++++++++++++++++++
2 files changed, 101 insertions(+)
create mode 100644 include/net/libeth/cache.h
diff --git a/scripts/kernel-doc b/scripts/kernel-doc
index 95a59ac78f82..d0cf9a2d82de 100755
--- a/scripts/kernel-doc
+++ b/scripts/kernel-doc
@@ -1155,6 +1155,7 @@ sub dump_struct($$) {
$members =~ s/\bstruct_group_attr\s*\(([^,]*,){2}/STRUCT_GROUP(/gos;
$members =~ s/\bstruct_group_tagged\s*\(([^,]*),([^,]*),/struct $1 $2; STRUCT_GROUP(/gos;
$members =~ s/\b__struct_group\s*\(([^,]*,){3}/STRUCT_GROUP(/gos;
+ $members =~ s/\blibeth_cacheline_group\s*\(([^,]*,)/struct { } $1; STRUCT_GROUP(/gos;
$members =~ s/\bSTRUCT_GROUP(\(((?:(?>[^)(]+)|(?1))*)\))[^;]*;/$2/gos;
my $args = qr{([^,)]+)};
diff --git a/include/net/libeth/cache.h b/include/net/libeth/cache.h
new file mode 100644
index 000000000000..5579240913d2
--- /dev/null
+++ b/include/net/libeth/cache.h
@@ -0,0 +1,100 @@
+/* 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(sizeof(long))
+
+/**
+ * libeth_cacheline_group - declare a cacheline-aligned field group
+ * @grp: name of the group (usually 'read_mostly', 'read_write', or 'cold')
+ * @...: struct fields inside the group
+ *
+ * Note that the whole group is cacheline-aligned, but the end marker is
+ * aligned to long, so that you pass the (almost) actual field size sum to
+ * the assertion macros below instead of CL-aligned values.
+ * Each cacheline group must be described in struct's kernel-doc.
+ */
+#define libeth_cacheline_group(grp, ...) \
+ struct_group(grp, \
+ __libeth_cacheline_group_begin(grp); \
+ __VA_ARGS__ \
+ __libeth_cacheline_group_end(grp); \
+ )
+
+/**
+ * libeth_cacheline_group_assert - make sure cacheline group size is expected
+ * @type: type of the structure containing the group
+ * @grp: group name inside the struct
+ * @sz: expected group size
+ */
+#if defined(CONFIG_64BIT) && SMP_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 || SMP_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 || SMP_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__)
+
+/**
+ * libeth_cacheline_struct_assert - make sure CL-based struct size is expected
+ * @type: type of the struct
+ * @...: from 1 to 3 CL group sizes (read-mostly, read-write, cold)
+ *
+ * When a struct contains several CL groups, it's difficult to predict its size
+ * on different architectures. The macro instead takes sizes of all of the
+ * groups the structure contains and generates the final struct size.
+ */
+#define libeth_cacheline_struct_assert(type, ...) \
+ __libeth_cacheline_struct_assert(type, __libeth_cls(__VA_ARGS__)); \
+ static_assert(__alignof(type) >= __LIBETH_LARGEST_ALIGN)
+
+/**
+ * libeth_cacheline_set_assert - make sure CL-based struct layout is expected
+ * @type: type of the struct
+ * @ro: expected size of the read-mostly group
+ * @rw: expected size of the read-write group
+ * @c: expected size of the cold group
+ *
+ * Check that each group size is expected and then do final struct size check.
+ */
+#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 */
--
2.45.1
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