[edk2-devel] [PATCH v8 07/10] OvmfPkg/SmmCpuFeaturesLib: call CPU hot-eject handler
Paolo Bonzini
pbonzini at redhat.com
Tue Feb 23 07:45:35 UTC 2021
On 22/02/21 15:53, Laszlo Ersek wrote:
>> +
>> + if (mCpuHotEjectData != NULL) {
>> + CPU_HOT_EJECT_HANDLER Handler;
>> +
>> + Handler = mCpuHotEjectData->Handler;
> This patch looks otherwise OK to me, but:
>
> In patch v8 08/10, we have a ReleaseMemoryFence(). (For now, it is only
> expressed as a MemoryFence() call; we'll make that more precise later.)
>
> (1) I think that should be paired with an AcquireMemoryFence() call,
> just before loading "mCpuHotEjectData->Handler" above -- for now, also
> expressed as a MemoryFence() call only.
In Linux terms, there is a control dependency here. However, it should
at least be a separate statement to load mCpuHotEjectData (which from my
EDK2 reminiscences should be a global) into a local variable. So
EjectData = mCPUHotEjectData;
// Optional AcquireMemoryFence here
if (EjectData != NULL) {
CPU_HOT_EJECT_HANDLER Handler;
Handler = EjectData->Handler;
if (Handler != NULL) {
Handler (CpuIndex);
}
}
Thanks,
Paolo
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