Ray Ni 62f2cf5784 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>		2021-02-26 11:51:37 +00:00
..
MpEqu.inc	UefiCpuPkg: Allow AP booting under SEV-ES	2020-08-17 02:46:39 +00:00
MpFuncs.nasm	UefiCpuPkg/MpInitLib: Use XADD to avoid lock acquire/release	2021-02-26 11:51:37 +00:00