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audk/OvmfPkg/CpuHotplugSmm/CpuHotplug.c

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/** @file
Root SMI handler for VCPU hotplug SMIs.
Copyright (c) 2020, Red Hat, Inc.
SPDX-License-Identifier: BSD-2-Clause-Patent
**/
#include <CpuHotPlugData.h> // CPU_HOT_PLUG_DATA
#include <IndustryStandard/Q35MchIch9.h> // ICH9_APM_CNT
#include <IndustryStandard/QemuCpuHotplug.h> // QEMU_CPUHP_CMD_GET_PENDING
#include <Library/BaseLib.h> // CpuDeadLoop()
#include <Library/DebugLib.h> // ASSERT()
#include <Library/MmServicesTableLib.h> // gMmst
#include <Library/PcdLib.h> // PcdGetBool()
#include <Library/SafeIntLib.h> // SafeUintnSub()
#include <Protocol/MmCpuIo.h> // EFI_MM_CPU_IO_PROTOCOL
#include <Protocol/SmmCpuService.h> // EFI_SMM_CPU_SERVICE_PROTOCOL
#include <Uefi/UefiBaseType.h> // EFI_STATUS
#include "ApicId.h" // APIC_ID
#include "QemuCpuhp.h" // QemuCpuhpWriteCpuSelector()
#include "Smbase.h" // SmbaseAllocatePostSmmPen()
//
// We use this protocol for accessing IO Ports.
//
STATIC EFI_MM_CPU_IO_PROTOCOL *mMmCpuIo;
//
// The following protocol is used to report the addition or removal of a CPU to
// the SMM CPU driver (PiSmmCpuDxeSmm).
//
STATIC EFI_SMM_CPU_SERVICE_PROTOCOL *mMmCpuService;
//
// This structure is a communication side-channel between the
// EFI_SMM_CPU_SERVICE_PROTOCOL consumer (i.e., this driver) and provider
// (i.e., PiSmmCpuDxeSmm).
//
STATIC CPU_HOT_PLUG_DATA *mCpuHotPlugData;
//
// SMRAM arrays for fetching the APIC IDs of processors with pending events (of
// known event types), for the time of just one MMI.
//
// The lifetimes of these arrays match that of this driver only because we
// don't want to allocate SMRAM at OS runtime, and potentially fail (or
// fragment the SMRAM map).
//
// These arrays provide room for ("possible CPU count" minus one) APIC IDs
// each, as we don't expect every possible CPU to appear, or disappear, in a
// single MMI. The numbers of used (populated) elements in the arrays are
// determined on every MMI separately.
//
STATIC APIC_ID *mPluggedApicIds;
STATIC APIC_ID *mToUnplugApicIds;
//
// Address of the non-SMRAM reserved memory page that contains the Post-SMM Pen
// for hot-added CPUs.
//
STATIC UINT32 mPostSmmPenAddress;
//
// Represents the registration of the CPU Hotplug MMI handler.
//
STATIC EFI_HANDLE mDispatchHandle;
/**
CPU Hotplug MMI handler function.
This is a root MMI handler.
@param[in] DispatchHandle The unique handle assigned to this handler by
EFI_MM_SYSTEM_TABLE.MmiHandlerRegister().
@param[in] Context Context passed in by
EFI_MM_SYSTEM_TABLE.MmiManage(). Due to
CpuHotplugMmi() being a root MMI handler,
Context is ASSERT()ed to be NULL.
@param[in,out] CommBuffer Ignored, due to CpuHotplugMmi() being a root
MMI handler.
@param[in,out] CommBufferSize Ignored, due to CpuHotplugMmi() being a root
MMI handler.
@retval EFI_SUCCESS The MMI was handled and the MMI
source was quiesced. When returned
by a non-root MMI handler,
EFI_SUCCESS terminates the
processing of MMI handlers in
EFI_MM_SYSTEM_TABLE.MmiManage().
For a root MMI handler (i.e., for
the present function too),
EFI_SUCCESS behaves identically to
EFI_WARN_INTERRUPT_SOURCE_QUIESCED,
as further root MMI handlers are
going to be called by
EFI_MM_SYSTEM_TABLE.MmiManage()
anyway.
@retval EFI_WARN_INTERRUPT_SOURCE_QUIESCED The MMI source has been quiesced,
but other handlers should still
be called.
@retval EFI_WARN_INTERRUPT_SOURCE_PENDING The MMI source is still pending,
and other handlers should still
be called.
@retval EFI_INTERRUPT_PENDING The MMI source could not be
quiesced.
**/
STATIC
EFI_STATUS
EFIAPI
CpuHotplugMmi (
IN EFI_HANDLE DispatchHandle,
IN CONST VOID *Context OPTIONAL,
IN OUT VOID *CommBuffer OPTIONAL,
IN OUT UINTN *CommBufferSize OPTIONAL
)
{
EFI_STATUS Status;
UINT8 ApmControl;
UINT32 PluggedCount;
UINT32 ToUnplugCount;
UINT32 PluggedIdx;
UINT32 NewSlot;
//
// Assert that we are entering this function due to our root MMI handler
// registration.
//
ASSERT (DispatchHandle == mDispatchHandle);
//
// When MmiManage() is invoked to process root MMI handlers, the caller (the
// MM Core) is expected to pass in a NULL Context. MmiManage() then passes
// the same NULL Context to individual handlers.
//
ASSERT (Context == NULL);
//
// Read the MMI command value from the APM Control Port, to see if this is an
// MMI we should care about.
//
Status = mMmCpuIo->Io.Read (mMmCpuIo, MM_IO_UINT8, ICH9_APM_CNT, 1,
&ApmControl);
if (EFI_ERROR (Status)) {
DEBUG ((DEBUG_ERROR, "%a: failed to read ICH9_APM_CNT: %r\n", __FUNCTION__,
Status));
//
// We couldn't even determine if the MMI was for us or not.
//
goto Fatal;
}
if (ApmControl != ICH9_APM_CNT_CPU_HOTPLUG) {
//
// The MMI is not for us.
//
return EFI_WARN_INTERRUPT_SOURCE_QUIESCED;
}
//
// Collect the CPUs with pending events.
//
Status = QemuCpuhpCollectApicIds (
mMmCpuIo,
mCpuHotPlugData->ArrayLength, // PossibleCpuCount
mCpuHotPlugData->ArrayLength - 1, // ApicIdCount
mPluggedApicIds,
&PluggedCount,
mToUnplugApicIds,
&ToUnplugCount
);
if (EFI_ERROR (Status)) {
goto Fatal;
}
if (ToUnplugCount > 0) {
DEBUG ((DEBUG_ERROR, "%a: hot-unplug is not supported yet\n",
__FUNCTION__));
goto Fatal;
}
//
// Process hot-added CPUs.
//
// The Post-SMM Pen need not be reinstalled multiple times within a single
// root MMI handling. Even reinstalling once per root MMI is only prudence;
// in theory installing the pen in the driver's entry point function should
// suffice.
//
SmbaseReinstallPostSmmPen (mPostSmmPenAddress);
PluggedIdx = 0;
NewSlot = 0;
while (PluggedIdx < PluggedCount) {
APIC_ID NewApicId;
UINT32 CheckSlot;
UINTN NewProcessorNumberByProtocol;
NewApicId = mPluggedApicIds[PluggedIdx];
//
// Check if the supposedly hot-added CPU is already known to us.
//
for (CheckSlot = 0;
CheckSlot < mCpuHotPlugData->ArrayLength;
CheckSlot++) {
if (mCpuHotPlugData->ApicId[CheckSlot] == NewApicId) {
break;
}
}
if (CheckSlot < mCpuHotPlugData->ArrayLength) {
DEBUG ((DEBUG_VERBOSE, "%a: APIC ID " FMT_APIC_ID " was hot-plugged "
"before; ignoring it\n", __FUNCTION__, NewApicId));
PluggedIdx++;
continue;
}
//
// Find the first empty slot in CPU_HOT_PLUG_DATA.
//
while (NewSlot < mCpuHotPlugData->ArrayLength &&
mCpuHotPlugData->ApicId[NewSlot] != MAX_UINT64) {
NewSlot++;
}
if (NewSlot == mCpuHotPlugData->ArrayLength) {
DEBUG ((DEBUG_ERROR, "%a: no room for APIC ID " FMT_APIC_ID "\n",
__FUNCTION__, NewApicId));
goto Fatal;
}
//
// Store the APIC ID of the new processor to the slot.
//
mCpuHotPlugData->ApicId[NewSlot] = NewApicId;
//
// Relocate the SMBASE of the new CPU.
//
Status = SmbaseRelocate (NewApicId, mCpuHotPlugData->SmBase[NewSlot],
mPostSmmPenAddress);
if (EFI_ERROR (Status)) {
goto RevokeNewSlot;
}
//
// Add the new CPU with EFI_SMM_CPU_SERVICE_PROTOCOL.
//
Status = mMmCpuService->AddProcessor (mMmCpuService, NewApicId,
&NewProcessorNumberByProtocol);
if (EFI_ERROR (Status)) {
DEBUG ((DEBUG_ERROR, "%a: AddProcessor(" FMT_APIC_ID "): %r\n",
__FUNCTION__, NewApicId, Status));
goto RevokeNewSlot;
}
DEBUG ((DEBUG_INFO, "%a: hot-added APIC ID " FMT_APIC_ID ", SMBASE 0x%Lx, "
"EFI_SMM_CPU_SERVICE_PROTOCOL assigned number %Lu\n", __FUNCTION__,
NewApicId, (UINT64)mCpuHotPlugData->SmBase[NewSlot],
(UINT64)NewProcessorNumberByProtocol));
NewSlot++;
PluggedIdx++;
}
//
// We've handled this MMI.
//
return EFI_SUCCESS;
RevokeNewSlot:
mCpuHotPlugData->ApicId[NewSlot] = MAX_UINT64;
Fatal:
ASSERT (FALSE);
CpuDeadLoop ();
//
// We couldn't handle this MMI.
//
return EFI_INTERRUPT_PENDING;
}
//
// Entry point function of this driver.
//
EFI_STATUS
EFIAPI
CpuHotplugEntry (
IN EFI_HANDLE ImageHandle,
IN EFI_SYSTEM_TABLE *SystemTable
)
{
EFI_STATUS Status;
UINTN Size;
//
// This module should only be included when SMM support is required.
//
ASSERT (FeaturePcdGet (PcdSmmSmramRequire));
//
// This driver depends on the dynamically detected "SMRAM at default SMBASE"
// feature.
//
if (!PcdGetBool (PcdQ35SmramAtDefaultSmbase)) {
return EFI_UNSUPPORTED;
}
//
// Errors from here on are fatal; we cannot allow the boot to proceed if we
// can't set up this driver to handle CPU hotplug.
//
// First, collect the protocols needed later. All of these protocols are
// listed in our module DEPEX.
//
Status = gMmst->MmLocateProtocol (&gEfiMmCpuIoProtocolGuid,
NULL /* Registration */, (VOID **)&mMmCpuIo);
if (EFI_ERROR (Status)) {
DEBUG ((DEBUG_ERROR, "%a: locate MmCpuIo: %r\n", __FUNCTION__, Status));
goto Fatal;
}
Status = gMmst->MmLocateProtocol (&gEfiSmmCpuServiceProtocolGuid,
NULL /* Registration */, (VOID **)&mMmCpuService);
if (EFI_ERROR (Status)) {
DEBUG ((DEBUG_ERROR, "%a: locate MmCpuService: %r\n", __FUNCTION__,
Status));
goto Fatal;
}
//
// Our DEPEX on EFI_SMM_CPU_SERVICE_PROTOCOL guarantees that PiSmmCpuDxeSmm
// has pointed PcdCpuHotPlugDataAddress to CPU_HOT_PLUG_DATA in SMRAM.
//
mCpuHotPlugData = (VOID *)(UINTN)PcdGet64 (PcdCpuHotPlugDataAddress);
if (mCpuHotPlugData == NULL) {
Status = EFI_NOT_FOUND;
DEBUG ((DEBUG_ERROR, "%a: CPU_HOT_PLUG_DATA: %r\n", __FUNCTION__, Status));
goto Fatal;
}
//
// If the possible CPU count is 1, there's nothing for this driver to do.
//
if (mCpuHotPlugData->ArrayLength == 1) {
return EFI_UNSUPPORTED;
}
//
// Allocate the data structures that depend on the possible CPU count.
//
if (RETURN_ERROR (SafeUintnSub (mCpuHotPlugData->ArrayLength, 1, &Size)) ||
RETURN_ERROR (SafeUintnMult (sizeof (APIC_ID), Size, &Size))) {
Status = EFI_ABORTED;
DEBUG ((DEBUG_ERROR, "%a: invalid CPU_HOT_PLUG_DATA\n", __FUNCTION__));
goto Fatal;
}
Status = gMmst->MmAllocatePool (EfiRuntimeServicesData, Size,
(VOID **)&mPluggedApicIds);
if (EFI_ERROR (Status)) {
DEBUG ((DEBUG_ERROR, "%a: MmAllocatePool(): %r\n", __FUNCTION__, Status));
goto Fatal;
}
Status = gMmst->MmAllocatePool (EfiRuntimeServicesData, Size,
(VOID **)&mToUnplugApicIds);
if (EFI_ERROR (Status)) {
DEBUG ((DEBUG_ERROR, "%a: MmAllocatePool(): %r\n", __FUNCTION__, Status));
goto ReleasePluggedApicIds;
}
//
// Allocate the Post-SMM Pen for hot-added CPUs.
//
Status = SmbaseAllocatePostSmmPen (&mPostSmmPenAddress,
SystemTable->BootServices);
if (EFI_ERROR (Status)) {
goto ReleaseToUnplugApicIds;
}
//
// Sanity-check the CPU hotplug interface.
//
// Both of the following features are part of QEMU 5.0, introduced primarily
// in commit range 3e08b2b9cb64..3a61c8db9d25:
//
// (a) the QEMU_CPUHP_CMD_GET_ARCH_ID command of the modern CPU hotplug
// interface,
//
// (b) the "SMRAM at default SMBASE" feature.
//
// From these, (b) is restricted to 5.0+ machine type versions, while (a)
// does not depend on machine type version. Because we ensured the stricter
// condition (b) through PcdQ35SmramAtDefaultSmbase above, the (a)
// QEMU_CPUHP_CMD_GET_ARCH_ID command must now be available too. While we
// can't verify the presence of precisely that command, we can still verify
// (sanity-check) that the modern interface is active, at least.
//
// Consult the "Typical usecases | Detecting and enabling modern CPU hotplug
// interface" section in QEMU's "docs/specs/acpi_cpu_hotplug.txt", on the
// following.
//
QemuCpuhpWriteCpuSelector (mMmCpuIo, 0);
QemuCpuhpWriteCpuSelector (mMmCpuIo, 0);
QemuCpuhpWriteCommand (mMmCpuIo, QEMU_CPUHP_CMD_GET_PENDING);
if (QemuCpuhpReadCommandData2 (mMmCpuIo) != 0) {
Status = EFI_NOT_FOUND;
DEBUG ((DEBUG_ERROR, "%a: modern CPU hotplug interface: %r\n",
__FUNCTION__, Status));
goto ReleasePostSmmPen;
}
//
// Register the handler for the CPU Hotplug MMI.
//
Status = gMmst->MmiHandlerRegister (
CpuHotplugMmi,
NULL, // HandlerType: root MMI handler
&mDispatchHandle
);
if (EFI_ERROR (Status)) {
DEBUG ((DEBUG_ERROR, "%a: MmiHandlerRegister(): %r\n", __FUNCTION__,
Status));
goto ReleasePostSmmPen;
}
//
// Install the handler for the hot-added CPUs' first SMI.
//
SmbaseInstallFirstSmiHandler ();
return EFI_SUCCESS;
ReleasePostSmmPen:
SmbaseReleasePostSmmPen (mPostSmmPenAddress, SystemTable->BootServices);
mPostSmmPenAddress = 0;
ReleaseToUnplugApicIds:
gMmst->MmFreePool (mToUnplugApicIds);
mToUnplugApicIds = NULL;
ReleasePluggedApicIds:
gMmst->MmFreePool (mPluggedApicIds);
mPluggedApicIds = NULL;
Fatal:
ASSERT (FALSE);
CpuDeadLoop ();
return Status;
}
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