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cpu: pretend AVX-512 is disabled on Darwin

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Darwin doesn't save/restore the AVX-512 mask registers when
processing a signal. Go generates lots of signals, which cause
the mask registers to randomly get clobbered. Better to pretend
that AVX-512 isn't supported.

Update golang/go#49233

Change-Id: I0dda77a6f205e10eefccd82e6f4f0f184dae42d9
Reviewed-on: https://go-review.googlesource.com/c/sys/+/361255
Trust: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Martin Möhrmann <martin@golang.org>
This commit is contained in:
Keith Randall
2021-11-03 14:27:36 -07:00
parent ae416a5f93
commit 7861aae155
2 changed files with 4 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
cpu/cpu_x86.go
View File

@@ -90,9 +90,10 @@ func archInit() {
osSupportsAVX = isSet(1, eax) && isSet(2, eax)
if runtime.GOOS == "darwin" {
// Check darwin commpage for AVX512 support. Necessary because:
// https://github.com/apple/darwin-xnu/blob/0a798f6738bc1db01281fc08ae024145e84df927/osfmk/i386/fpu.c#L175-L201
osSupportsAVX512 = osSupportsAVX && darwinSupportsAVX512()
// 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
} else {
// Check if OPMASK and ZMM registers have OS support.
osSupportsAVX512 = osSupportsAVX && isSet(5, eax) && isSet(6, eax) && isSet(7, eax)

24
cpu/cpu_x86.s
View File

@@ -26,27 +26,3 @@ TEXT ·xgetbv(SB),NOSPLIT,$0-8
MOVL AX, eax+0(FP)
MOVL DX, edx+4(FP)
RET
// func darwinSupportsAVX512() bool
TEXT ·darwinSupportsAVX512(SB), NOSPLIT, $0-1
MOVB $0, ret+0(FP) // default to false
#ifdef GOOS_darwin // return if not darwin
#ifdef GOARCH_amd64 // return if not amd64
// These values from:
// https://github.com/apple/darwin-xnu/blob/xnu-4570.1.46/osfmk/i386/cpu_capabilities.h
#define commpage64_base_address 0x00007fffffe00000
#define commpage64_cpu_capabilities64 (commpage64_base_address+0x010)
#define commpage64_version (commpage64_base_address+0x01E)
#define hasAVX512F 0x0000004000000000
MOVQ $commpage64_version, BX
CMPW (BX), $13 // cpu_capabilities64 undefined in versions < 13
JL no_avx512
MOVQ $commpage64_cpu_capabilities64, BX
MOVQ $hasAVX512F, CX
TESTQ (BX), CX
JZ no_avx512
MOVB $1, ret+0(FP)
no_avx512:
#endif
#endif
RET