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cpu: conditionally re-enable AVX512 support on darwin/amd64

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Darwin opmask clobbering bug was fixed in kernel version 21.3.0
as released in MacOS 12.2.0. This commit resolves issue by
checking for Darwin AVX512 support via a sysctl call with the
addition of a kernel minimum version check.

The kernel version check is completed without adding new
dependencies to x/sys/cpu. A sysctl call is accomplished by
copying a minimal amount of code from x/sys/unix, to retrieve
only the needed KERN_OSRELEASE value. This code is structured
in the same manner as an existing analogous AIX/PPC64 syscall.

The resulting dotted version string value is then parsed for
numeric comparison with a dependency free function.

All code in this contribution is structured to ease removal of
the special darwin/amd64 codepaths when that OS/arch combination
is eventually no longer supported by golang.

Resolves issue: golang/go#49233, reinstates fix for issue: golang/go#43089

Change-Id: I4755fc8b3865eb6562b0959ecc910e2c46ac6cb4
Reviewed-on: https://go-review.googlesource.com/c/sys/+/620256
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: vsivsi@yahoo.com <vsivsi@yahoo.com>
This commit is contained in:
Vaughn Iverson
2024-11-04 23:17:32 +00:00
committed by Keith Randall
parent 054f1fcdf7
commit 8f2aa9fb48
8 changed files with 192 additions and 13 deletions
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cpu/cpu_x86.go
+2 -4
View File
@@ -92,10 +92,8 @@ func archInit() {
osSupportsAVX = isSet(1, eax) && isSet(2, eax)
if runtime.GOOS == "darwin" {
// Darwin doesn't save/restore AVX-512 mask registers correctly across signal handlers.
// Since users can't rely on mask register contents, let's not advertise AVX-512 support.
// See issue 49233.
osSupportsAVX512 = false
// Darwin requires special AVX512 checks, see cpu_darwin_x86.go
osSupportsAVX512 = osSupportsAVX && darwinSupportsAVX512()
} else {
// Check if OPMASK and ZMM registers have OS support.
osSupportsAVX512 = osSupportsAVX && isSet(5, eax) && isSet(6, eax) && isSet(7, eax)