diff options
| -rw-r--r-- | OvmfPkg/CpuHotplugSmm/CpuHotplug.c | 111 | ||||
| -rw-r--r-- | OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h | 1 |
2 files changed, 106 insertions, 6 deletions
diff --git a/OvmfPkg/CpuHotplugSmm/CpuHotplug.c b/OvmfPkg/CpuHotplugSmm/CpuHotplug.c index 2eeb4567a2..2c768f89f1 100644 --- a/OvmfPkg/CpuHotplugSmm/CpuHotplug.c +++ b/OvmfPkg/CpuHotplugSmm/CpuHotplug.c @@ -18,6 +18,7 @@ #include <Pcd/CpuHotEjectData.h> // CPU_HOT_EJECT_DATA
#include <Protocol/MmCpuIo.h> // EFI_MM_CPU_IO_PROTOCOL
#include <Protocol/SmmCpuService.h> // EFI_SMM_CPU_SERVICE_PROTOCOL
+#include <Register/Intel/ArchitecturalMsr.h> // MSR_IA32_APIC_BASE_REGISTER
#include <Uefi/UefiBaseType.h> // EFI_STATUS
#include "ApicId.h" // APIC_ID
@@ -193,12 +194,40 @@ RevokeNewSlot: }
/**
+ EjectCpu needs to know the BSP at SMI exit at a point when
+ some of the EFI_SMM_CPU_SERVICE_PROTOCOL state has been torn
+ down.
+ Reuse the logic from OvmfPkg::PlatformSmmBspElection() to
+ do that.
+
+ @retval TRUE If the CPU executing this function is the BSP.
+
+ @retval FALSE If the CPU executing this function is an AP.
+**/
+STATIC
+BOOLEAN
+CheckIfBsp (
+ VOID
+ )
+{
+ MSR_IA32_APIC_BASE_REGISTER ApicBaseMsr;
+ BOOLEAN IsBsp;
+
+ ApicBaseMsr.Uint64 = AsmReadMsr64 (MSR_IA32_APIC_BASE);
+ IsBsp = (BOOLEAN)(ApicBaseMsr.Bits.BSP == 1);
+ return IsBsp;
+}
+
+/**
CPU Hot-eject handler, called from SmmCpuFeaturesRendezvousExit()
on each CPU at exit from SMM.
- If, the executing CPU is not being ejected, nothing to be done.
+ If, the executing CPU is neither the BSP, nor being ejected, nothing
+ to be done.
If, the executing CPU is being ejected, wait in a halted loop
until ejected.
+ If, the executing CPU is the BSP, set QEMU CPU status to eject
+ for CPUs being ejected.
@param[in] ProcessorNum ProcessorNum denotes the CPU exiting SMM,
and will be used as an index into
@@ -214,6 +243,81 @@ EjectCpu ( {
UINT64 QemuSelector;
+ if (CheckIfBsp ()) {
+ UINT32 Idx;
+
+ for (Idx = 0; Idx < mCpuHotEjectData->ArrayLength; Idx++) {
+ QemuSelector = mCpuHotEjectData->QemuSelectorMap[Idx];
+
+ if (QemuSelector != CPU_EJECT_QEMU_SELECTOR_INVALID) {
+ //
+ // This to-be-ejected-CPU has already received the BSP's SMI exit
+ // signal and will execute SmmCpuFeaturesRendezvousExit()
+ // followed by this callback or is already penned in the
+ // CpuSleep() loop below.
+ //
+ // Tell QEMU to context-switch it out.
+ //
+ QemuCpuhpWriteCpuSelector (mMmCpuIo, (UINT32) QemuSelector);
+ QemuCpuhpWriteCpuStatus (mMmCpuIo, QEMU_CPUHP_STAT_EJECT);
+
+ //
+ // Now that we've ejected the CPU corresponding to QemuSelectorMap[Idx],
+ // clear its eject status to ensure that an invalid future SMI does
+ // not end up trying a spurious eject or a newly hotplugged CPU does
+ // not get penned in the CpuSleep() loop.
+ //
+ // Note that the QemuCpuhpWriteCpuStatus() command above is a write to
+ // a different address space and uses the EFI_MM_CPU_IO_PROTOCOL.
+ //
+ // This means that we are guaranteed that the following assignment
+ // will not be reordered before the eject. And, so we can safely
+ // do this write here.
+ //
+ mCpuHotEjectData->QemuSelectorMap[Idx] =
+ CPU_EJECT_QEMU_SELECTOR_INVALID;
+
+ DEBUG ((DEBUG_INFO, "%a: Unplugged ProcessorNum %u, "
+ "QemuSelector %Lu\n", __FUNCTION__, Idx, QemuSelector));
+ }
+ }
+
+ //
+ // We are done until the next hot-unplug; clear the handler.
+ //
+ // mCpuHotEjectData->Handler is a NOP for any CPU not under ejection.
+ // So, once we are done with all the ejections, we can safely reset it
+ // here since any CPU dereferencing it would only see either the old
+ // or the new value (since it is aligned at a natural boundary.)
+ //
+ mCpuHotEjectData->Handler = NULL;
+ return;
+ }
+
+ //
+ // Reached only on APs
+ //
+
+ //
+ // mCpuHotEjectData->QemuSelectorMap[ProcessorNum] is updated
+ // on the BSP in the ongoing SMI at two places:
+ //
+ // - UnplugCpus() where the BSP determines if a CPU is under ejection
+ // or not. As a comment in UnplugCpus() at set-up, and in
+ // SmmCpuFeaturesRendezvousExit() where it is dereferenced describe,
+ // any such updates are guaranteed to be ordered-before the
+ // dereference below.
+ //
+ // - EjectCpu() on the BSP (above) updates QemuSelectorMap[ProcessorNum]
+ // for a CPU once it's ejected.
+ //
+ // The CPU under ejection: might be executing anywhere between the
+ // AllCpusInSync loop in SmiRendezvous(), to about to dereference
+ // QemuSelectorMap[ProcessorNum].
+ // As described in the comment above where we do the reset, this
+ // is not a problem since the ejected CPU never sees the after value.
+ // CPUs not-under ejection: never see any changes so they are fine.
+ //
QemuSelector = mCpuHotEjectData->QemuSelectorMap[ProcessorNum];
if (QemuSelector == CPU_EJECT_QEMU_SELECTOR_INVALID) {
return;
@@ -495,11 +599,6 @@ CpuHotplugMmi ( if (EFI_ERROR (Status)) {
goto Fatal;
}
- if (ToUnplugCount > 0) {
- DEBUG ((DEBUG_ERROR, "%a: hot-unplug is not supported yet\n",
- __FUNCTION__));
- goto Fatal;
- }
if (PluggedCount > 0) {
Status = ProcessHotAddedCpus (mPluggedApicIds, PluggedCount);
diff --git a/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h b/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h index 2ec7a107a6..d0e83102c1 100644 --- a/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h +++ b/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h @@ -34,6 +34,7 @@ #define QEMU_CPUHP_STAT_ENABLED BIT0
#define QEMU_CPUHP_STAT_INSERT BIT1
#define QEMU_CPUHP_STAT_REMOVE BIT2
+#define QEMU_CPUHP_STAT_EJECT BIT3
#define QEMU_CPUHP_STAT_FW_REMOVE BIT4
#define QEMU_CPUHP_RW_CMD_DATA 0x8
|