In a system which has multiple cores, current set register value task costs
huge times.
After investigation, current set MSR task costs most of the times. Current
logic uses
SpinLock to let set MSR task as an single thread task for all cores. Because
MSR has
scope attribute which may cause GP fault if multiple APs set MSR at the same
time,
current logic use an easiest solution (use SpinLock) to avoid this issue, but
it will
cost huge times.
In order to fix this performance issue, new solution will set MSRs base on
their scope
attribute. After this, the SpinLock will not needed. Without SpinLock, new
issue raised
which is caused by MSR dependence. For example, MSR A depends on MSR B which
means MSR A
must been set after MSR B has been set. Also MSR B is package scope level and
MSR A is
thread scope level. If system has multiple threads, Thread 1 needs to set the
thread level
MSRs and thread 2 needs to set thread and package level MSRs. Set MSRs task for
thread 1
and thread 2 like below:
Thread 1 Thread 2
MSR B N Y
MSR A Y Y
If driver don't control execute MSR order, for thread 1, it will execute MSR A
first, but
at this time, MSR B not been executed yet by thread 2. system may trig
exception at this
time.
In order to fix the above issue, driver introduces semaphore logic to control
the MSR
execute sequence. For the above case, a semaphore will be add between MSR A and
B for
all threads. Semaphore has scope info for it. The possible scope value is core
or package.
For each thread, when it meets a semaphore during it set registers, it will 1)
release
semaphore (+1) for each threads in this core or package(based on the scope info
for this
semaphore) 2) acquire semaphore (-1) for all the threads in this core or
package(based
on the scope info for this semaphore). With these two steps, driver can control
MSR
sequence. Sample code logic like below:
//
// First increase semaphore count by 1 for processors in this package.
//
for (ProcessorIndex = 0; ProcessorIndex < PackageThreadsCount ;
ProcessorIndex ++) {
LibReleaseSemaphore ((UINT32 *) &SemaphorePtr[PackageOffset +
ProcessorIndex]);
}
//
// Second, check whether the count has reach the check number.
//
for (ProcessorIndex = 0; ProcessorIndex < ValidApCount; ProcessorIndex ++) {
LibWaitForSemaphore (&SemaphorePtr[ApOffset]);
}
Platform Requirement:
1. This change requires register MSR setting base on MSR scope info. If still
register MSR
for all threads, exception may raised.
Known limitation:
1. Current CpuFeatures driver supports DXE instance and PEI instance. But
semaphore logic
requires Aps execute in async mode which is not supported by PEI driver. So
CpuFeature
PEI instance not works after this change. We plan to support async mode for
PEI in phase
2 for this task.
2. Current execute MSR task code in duplicated in PiSmmCpuDxeSmm driver and
RegisterCpuFeaturesLib library because the schedule limitation. Will merge
the code to
RegisterCpuFeaturesLib and export as an API in phase 2 for this task.
Extra Notes:
I will send the other patch to set MSR base on scope info and check in it
before check in
this serial.
Cc: Ruiyu Ni <[email protected]>
Cc: Laszlo Ersek <[email protected]>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Eric Dong <[email protected]>
Eric Dong (4):
UefiCpuPkg/Include/AcpiCpuData.h: Add Semaphore related Information.
UefiCpuPkg/RegisterCpuFeaturesLib.h: Add new dependence types.
UefiCpuPkg/RegisterCpuFeaturesLib: Add logic to support semaphore
type.
UefiCpuPkg/PiSmmCpuDxeSmm: Add logic to support semaphore type.
UefiCpuPkg/Include/AcpiCpuData.h | 23 +-
.../Include/Library/RegisterCpuFeaturesLib.h | 25 +-
.../RegisterCpuFeaturesLib/CpuFeaturesInitialize.c | 324 ++++++++++++---
.../DxeRegisterCpuFeaturesLib.c | 71 +++-
.../DxeRegisterCpuFeaturesLib.inf | 3 +
.../PeiRegisterCpuFeaturesLib.c | 55 ++-
.../PeiRegisterCpuFeaturesLib.inf | 1 +
.../RegisterCpuFeaturesLib/RegisterCpuFeatures.h | 51 ++-
.../RegisterCpuFeaturesLib.c | 452 ++++++++++++++++++---
UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c | 316 +++++++-------
UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 3 -
UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h | 3 +-
12 files changed, 1063 insertions(+), 264 deletions(-)
--
2.15.0.windows.1
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