git: 32d1f18865ab - main - libc/aarch64: Add memset for a 64 byte dc zva

The branch main has been updated by andrew:

URL: https://cgit.FreeBSD.org/src/commit/?id=32d1f18865abe94d351a6f178a93b7195595ec69

commit 32d1f18865abe94d351a6f178a93b7195595ec69
Author:     Andrew Turner <andrew@FreeBSD.org>
AuthorDate: 2026-02-03 14:01:32 +0000
Commit:     Andrew Turner <andrew@FreeBSD.org>
CommitDate: 2026-02-03 17:11:51 +0000

    libc/aarch64: Add memset for a 64 byte dc zva
    
    On arm64 we can use the "dc zva" instruction to zero memory. The CPU
    tells software if the instruction is implemented, and if so the size
    and alignment it will use.
    
    When the size is 64-bytes the Arm Optimized Routines implementation of
    memset can use dc zva to zero memory, and has a build flag to skip
    checking.
    
    Use this flag to build a version of memset that will be used when this
    assumption is true.
    
    Sponsored by:   Arm Ltd
    Differential Revision:  https://reviews.freebsd.org/D54776
---
 lib/libc/aarch64/string/Makefile.inc      |  4 +++-
 lib/libc/aarch64/string/memset_resolver.c | 13 +++++++++++++
 lib/libc/aarch64/string/memset_zva64.S    |  4 ++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/lib/libc/aarch64/string/Makefile.inc b/lib/libc/aarch64/string/Makefile.inc
index 20a844f80e17..bc05e849aa20 100644
--- a/lib/libc/aarch64/string/Makefile.inc
+++ b/lib/libc/aarch64/string/Makefile.inc
@@ -42,7 +42,8 @@ MDSRCS+= \
 	memcpy_resolver.c \
 	memmove_resolver.c \
 	memset.S \
-	memset_resolver.c
+	memset_resolver.c \
+	memset_zva64.S
 
 #
 # Add the above functions. Generate an asm file that includes the needed
@@ -77,3 +78,4 @@ CFLAGS.${FILE}+=-I${SRCTOP}/contrib/arm-optimized-routines/string
 CFLAGS.memchr.S+=-I${SRCTOP}/contrib/arm-optimized-routines/string
 CFLAGS.memcpy.S+=-I${SRCTOP}/contrib/arm-optimized-routines/string
 CFLAGS.memset.S+=-I${SRCTOP}/contrib/arm-optimized-routines/string
+CFLAGS.memset_zva64.S+=-I${SRCTOP}/contrib/arm-optimized-routines/string
diff --git a/lib/libc/aarch64/string/memset_resolver.c b/lib/libc/aarch64/string/memset_resolver.c
index 34ca98aa1d34..277e8c177de9 100644
--- a/lib/libc/aarch64/string/memset_resolver.c
+++ b/lib/libc/aarch64/string/memset_resolver.c
@@ -25,18 +25,31 @@
  * SUCH DAMAGE.
  */
 #include <sys/types.h>
+
+#include <machine/armreg.h>
 #include <machine/ifunc.h>
 
 #include <elf.h>
 
 void *__memset_aarch64(void *, int, size_t);
+void *__memset_aarch64_zva64(void *, int, size_t);
 void *__memset_aarch64_mops(void *, int, size_t);
 
 DEFINE_UIFUNC(, void *, memset, (void *, int, size_t))
 {
+	uint64_t dczid;
+
 	if (ifunc_arg->_hwcap2 & HWCAP2_MOPS)
 		return (__memset_aarch64_mops);
 
+	/*
+	 * Check for the DC ZVA instruction, and it will
+	 * zero 64 bytes (4 * 4byte words).
+	 */
+	dczid = READ_SPECIALREG(dczid_el0);
+	if ((dczid & DCZID_DZP) == 0 && DCZID_BS_SIZE(dczid) == 4)
+		return (__memset_aarch64_zva64);
+
 	return (__memset_aarch64);
 }
 
diff --git a/lib/libc/aarch64/string/memset_zva64.S b/lib/libc/aarch64/string/memset_zva64.S
new file mode 100644
index 000000000000..7f1cf6ba577a
--- /dev/null
+++ b/lib/libc/aarch64/string/memset_zva64.S
@@ -0,0 +1,4 @@
+/* Used when we know we have a 64-byte dc zva instruction */
+#define	__memset_aarch64	__memset_aarch64_zva64
+#define	SKIP_ZVA_CHECK
+#include "aarch64/memset.S"