Call the CPU hot-eject handler if one is installed. The condition for installation is (PcdCpuMaxLogicalProcessorNumber > 1), and there's a hot-unplug request.
The handler is called from SmmCpuFeaturesRendezvousExit(), which is in-turn called at the tail-end of SmiRendezvous() after the BSP has signalled an SMI exit via the "AllCpusInSync" loop. Cc: Laszlo Ersek <ler...@redhat.com> Cc: Jordan Justen <jordan.l.jus...@intel.com> Cc: Ard Biesheuvel <ard.biesheu...@arm.com> Cc: Igor Mammedov <imamm...@redhat.com> Cc: Boris Ostrovsky <boris.ostrov...@oracle.com> Cc: Aaron Young <aaron.yo...@oracle.com> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3132 Signed-off-by: Ankur Arora <ankur.a.ar...@oracle.com> --- Notes: Addresses the following comments from v8: (1) Add a MemoryFence() before accessing mCpuHotEjctData->Handler (and comment to that effect.) .../Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.c | 34 ++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/OvmfPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.c b/OvmfPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.c index 5c025bc717c3..fdf2380974fa 100644 --- a/OvmfPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.c +++ b/OvmfPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.c @@ -452,6 +452,40 @@ SmmCpuFeaturesRendezvousExit ( IN UINTN CpuIndex ) { + // + // We only call the Handler if CPU hot-eject is enabled + // (PcdCpuMaxLogicalProcessorNumber > 1), and hot-eject is needed + // in this SMI exit (otherwise mCpuHotEjectData->Handler is not armed.) + // + + if (mCpuHotEjectData != NULL) { + CPU_HOT_EJECT_HANDLER Handler; + + // + // As the comment above mentions, mCpuHotEjectData->Handler might be + // written to on the BSP as part of handling of the CPU-ejection. + // + // We know that any initial assignment to mCpuHotEjectData->Handler + // (on the BSP, in the CpuHotplugMmi() context) is ordered-before the + // load below, since it is guaranteed to happen before the + // control-dependency of the BSP's SMI exit signal -- by way of a store + // to AllCpusInSync (on the BSP, in BspHandler()) and the corresponding + // AllCpusInSync loop (on the APs, in SmiRendezvous()) which depends on + // that store. + // + // This guarantees that these pieces of code can never execute + // simultaneously. In addition, we ensure that the following load is + // ordered-after the AllCpusInSync loop by using a MemoryFence() with + // acquire semantics. + // + MemoryFence(); + + Handler = mCpuHotEjectData->Handler; + + if (Handler != NULL) { + Handler (CpuIndex); + } + } } /** -- 2.9.3 -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#72709): https://edk2.groups.io/g/devel/message/72709 Mute This Topic: https://groups.io/mt/81273609/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
