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| author | Ray Ni <ray.ni@intel.com> | 2021-01-28 11:42:43 +0800 |
|---|---|---|
| committer | mergify[bot] <37929162+mergify[bot]@users.noreply.github.com> | 2021-02-26 11:51:37 +0000 |
| commit | 62f2cf57840e3b08122b6326b0ed9f4b25ce15d9 (patch) | |
| tree | 5562d04acc951974fbaaf5a90926854e2b3ee1cf /UefiCpuPkg | |
| parent | 6ffbb3581ab7c25a35041bac03b760af54f852bf (diff) | |
| download | edk2-62f2cf57840e3b08122b6326b0ed9f4b25ce15d9.tar.gz edk2-62f2cf57840e3b08122b6326b0ed9f4b25ce15d9.tar.bz2 edk2-62f2cf57840e3b08122b6326b0ed9f4b25ce15d9.zip | |
UefiCpuPkg/MpInitLib: Use XADD to avoid lock acquire/release
When AP firstly wakes up, MpFuncs.nasm contains below logic to assign
an unique ApIndex to each AP according to who comes first:
---ASM---
TestLock:
xchg [edi], eax
cmp eax, NotVacantFlag
jz TestLock
mov ecx, esi
add ecx, ApIndexLocation
inc dword [ecx]
mov ebx, [ecx]
Releaselock:
mov eax, VacantFlag
xchg [edi], eax
---ASM END---
"lock inc" cannot be used to increase ApIndex because not only the
global ApIndex should be increased, but also the result should be
stored to a local general purpose register EBX.
This patch learns from the NASM implementation of
InternalSyncIncrement() to use "XADD" instruction which can increase
the global ApIndex and store the original ApIndex to EBX in one
instruction.
With this patch, OVMF when running in a 255 threads QEMU spends about
one second to wakeup all APs. Original implementation needs more than
10 seconds.
Signed-off-by: Ray Ni <ray.ni@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Diffstat (limited to 'UefiCpuPkg')
| -rw-r--r-- | UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm | 20 | ||||
| -rw-r--r-- | UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm | 18 |
2 files changed, 12 insertions, 26 deletions
diff --git a/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm b/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm index 7e81d24aa6..2eaddc93bc 100644 --- a/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm +++ b/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm @@ -1,5 +1,5 @@ ;------------------------------------------------------------------------------ ;
-; Copyright (c) 2015 - 2019, Intel Corporation. All rights reserved.<BR>
+; Copyright (c) 2015 - 2021, Intel Corporation. All rights reserved.<BR>
; SPDX-License-Identifier: BSD-2-Clause-Patent
;
; Module Name:
@@ -125,19 +125,11 @@ SkipEnableExecuteDisable: add edi, LockLocation
mov eax, NotVacantFlag
-TestLock:
- xchg [edi], eax
- cmp eax, NotVacantFlag
- jz TestLock
-
- mov ecx, esi
- add ecx, ApIndexLocation
- inc dword [ecx]
- mov ebx, [ecx]
-
-Releaselock:
- mov eax, VacantFlag
- xchg [edi], eax
+ mov edi, esi
+ add edi, ApIndexLocation
+ mov ebx, 1
+ lock xadd dword [edi], ebx ; EBX = ApIndex++
+ inc ebx ; EBX is CpuNumber
mov edi, esi
add edi, StackSizeLocation
diff --git a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm index aecfd07bc0..5b588f2dcb 100644 --- a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm +++ b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm @@ -1,5 +1,5 @@ ;------------------------------------------------------------------------------ ;
-; Copyright (c) 2015 - 2019, Intel Corporation. All rights reserved.<BR>
+; Copyright (c) 2015 - 2021, Intel Corporation. All rights reserved.<BR>
; SPDX-License-Identifier: BSD-2-Clause-Patent
;
; Module Name:
@@ -161,18 +161,12 @@ LongModeStart: add edi, LockLocation
mov rax, NotVacantFlag
-TestLock:
- xchg qword [edi], rax
- cmp rax, NotVacantFlag
- jz TestLock
-
- lea ecx, [esi + ApIndexLocation]
- inc dword [ecx]
- mov ebx, [ecx]
+ mov edi, esi
+ add edi, ApIndexLocation
+ mov ebx, 1
+ lock xadd dword [edi], ebx ; EBX = ApIndex++
+ inc ebx ; EBX is CpuNumber
-Releaselock:
- mov rax, VacantFlag
- xchg qword [edi], rax
; program stack
mov edi, esi
add edi, StackSizeLocation
|