audk/OvmfPkg/SmmControl2Dxe/SmiFeatures.h

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OvmfPkg/SmmControl2Dxe: select broadcast SMI if available When writing to IO port 0xB2 (ICH9_APM_CNT), QEMU by default injects an SMI only on the VCPU that is writing the port. This has exposed corner cases and strange behavior with edk2 code, which generally expects a software SMI to affect all CPUs at once. We've experienced instability despite the fact that OVMF sets PcdCpuSmmApSyncTimeout and PcdCpuSmmSyncMode differently from the UefiCpuPkg defaults, such that they match QEMU's unicast SMIs better. (Refer to edk2 commits 9b1e378811ff and bb0f18b0bce6.) Using the new fw_cfg-based SMI feature negotiation in QEMU (see commits 50de920b372b "hw/isa/lpc_ich9: add SMI feature negotiation via fw_cfg" and 5ce45c7a2b15 "hw/isa/lpc_ich9: add broadcast SMI feature"), we can ask QEMU to broadcast SMIs. Extensive testing from earlier proves that broadcast SMIs are only reliable if we use the UefiCpuPkg defaults for the above PCDs. With those settings however, the broadcast is very reliable -- the most reliable configuration encountered thus far. Therefore negotiate broadcast SMIs with QEMU, and if the negotiation is successful, dynamically revert the PCDs to the UefiCpuPkg defaults. Setting the PCDs in this module is safe: - only PiSmmCpuDxeSmm consumes them, - PiSmmCpuDxeSmm is a DXE_SMM_DRIVER, launched by the SMM_CORE (MdeModulePkg/Core/PiSmmCore/PiSmmCore.inf), - the SMM_CORE is launched by the SMM IPL runtime DXE driver (MdeModulePkg/Core/PiSmmCore/PiSmmIpl.inf), - the SMM IPL has a DEPEX on EFI_SMM_CONTROL2_PROTOCOL, - OvmfPkg/SmmControl2Dxe produces that protocol. The end result is that PiSmmCpuDxeSmm cannot be dispatched before SmmControl2Dxe installs EFI_SMM_CONTROL2_PROTOCOL and returns from its entry point. Hence we can set the PCD's consumed by PiSmmCpuDxeSmm in SmmControl2Dxe. Cc: Jordan Justen <jordan.l.justen@intel.com> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=230 Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Laszlo Ersek <lersek@redhat.com> Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
2016-11-30 20:06:34 +01:00
/**@file
Negotiate SMI features with QEMU, and configure UefiCpuPkg/PiSmmCpuDxeSmm
accordingly.
Copyright (C) 2016-2017, Red Hat, Inc.
SPDX-License-Identifier: BSD-2-Clause-Patent
OvmfPkg/SmmControl2Dxe: select broadcast SMI if available When writing to IO port 0xB2 (ICH9_APM_CNT), QEMU by default injects an SMI only on the VCPU that is writing the port. This has exposed corner cases and strange behavior with edk2 code, which generally expects a software SMI to affect all CPUs at once. We've experienced instability despite the fact that OVMF sets PcdCpuSmmApSyncTimeout and PcdCpuSmmSyncMode differently from the UefiCpuPkg defaults, such that they match QEMU's unicast SMIs better. (Refer to edk2 commits 9b1e378811ff and bb0f18b0bce6.) Using the new fw_cfg-based SMI feature negotiation in QEMU (see commits 50de920b372b "hw/isa/lpc_ich9: add SMI feature negotiation via fw_cfg" and 5ce45c7a2b15 "hw/isa/lpc_ich9: add broadcast SMI feature"), we can ask QEMU to broadcast SMIs. Extensive testing from earlier proves that broadcast SMIs are only reliable if we use the UefiCpuPkg defaults for the above PCDs. With those settings however, the broadcast is very reliable -- the most reliable configuration encountered thus far. Therefore negotiate broadcast SMIs with QEMU, and if the negotiation is successful, dynamically revert the PCDs to the UefiCpuPkg defaults. Setting the PCDs in this module is safe: - only PiSmmCpuDxeSmm consumes them, - PiSmmCpuDxeSmm is a DXE_SMM_DRIVER, launched by the SMM_CORE (MdeModulePkg/Core/PiSmmCore/PiSmmCore.inf), - the SMM_CORE is launched by the SMM IPL runtime DXE driver (MdeModulePkg/Core/PiSmmCore/PiSmmIpl.inf), - the SMM IPL has a DEPEX on EFI_SMM_CONTROL2_PROTOCOL, - OvmfPkg/SmmControl2Dxe produces that protocol. The end result is that PiSmmCpuDxeSmm cannot be dispatched before SmmControl2Dxe installs EFI_SMM_CONTROL2_PROTOCOL and returns from its entry point. Hence we can set the PCD's consumed by PiSmmCpuDxeSmm in SmmControl2Dxe. Cc: Jordan Justen <jordan.l.justen@intel.com> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=230 Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Laszlo Ersek <lersek@redhat.com> Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
2016-11-30 20:06:34 +01:00
**/
#ifndef __SMI_FEATURES_H__
#define __SMI_FEATURES_H__
#include <Protocol/S3SaveState.h>
/**
Negotiate SMI features with QEMU.
@retval FALSE If SMI feature negotiation is not supported by QEMU. This is
not an error, it just means that SaveSmiFeatures() should not
be called.
@retval TRUE SMI feature negotiation is supported, and it has completed
successfully as well. (Failure to negotiate is a fatal error
and the function never returns in that case.)
**/
BOOLEAN
NegotiateSmiFeatures (
VOID
);
/**
Append a boot script fragment that will re-select the previously negotiated
SMI features during S3 resume.
**/
VOID
SaveSmiFeatures (
VOID
OvmfPkg/SmmControl2Dxe: select broadcast SMI if available When writing to IO port 0xB2 (ICH9_APM_CNT), QEMU by default injects an SMI only on the VCPU that is writing the port. This has exposed corner cases and strange behavior with edk2 code, which generally expects a software SMI to affect all CPUs at once. We've experienced instability despite the fact that OVMF sets PcdCpuSmmApSyncTimeout and PcdCpuSmmSyncMode differently from the UefiCpuPkg defaults, such that they match QEMU's unicast SMIs better. (Refer to edk2 commits 9b1e378811ff and bb0f18b0bce6.) Using the new fw_cfg-based SMI feature negotiation in QEMU (see commits 50de920b372b "hw/isa/lpc_ich9: add SMI feature negotiation via fw_cfg" and 5ce45c7a2b15 "hw/isa/lpc_ich9: add broadcast SMI feature"), we can ask QEMU to broadcast SMIs. Extensive testing from earlier proves that broadcast SMIs are only reliable if we use the UefiCpuPkg defaults for the above PCDs. With those settings however, the broadcast is very reliable -- the most reliable configuration encountered thus far. Therefore negotiate broadcast SMIs with QEMU, and if the negotiation is successful, dynamically revert the PCDs to the UefiCpuPkg defaults. Setting the PCDs in this module is safe: - only PiSmmCpuDxeSmm consumes them, - PiSmmCpuDxeSmm is a DXE_SMM_DRIVER, launched by the SMM_CORE (MdeModulePkg/Core/PiSmmCore/PiSmmCore.inf), - the SMM_CORE is launched by the SMM IPL runtime DXE driver (MdeModulePkg/Core/PiSmmCore/PiSmmIpl.inf), - the SMM IPL has a DEPEX on EFI_SMM_CONTROL2_PROTOCOL, - OvmfPkg/SmmControl2Dxe produces that protocol. The end result is that PiSmmCpuDxeSmm cannot be dispatched before SmmControl2Dxe installs EFI_SMM_CONTROL2_PROTOCOL and returns from its entry point. Hence we can set the PCD's consumed by PiSmmCpuDxeSmm in SmmControl2Dxe. Cc: Jordan Justen <jordan.l.justen@intel.com> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=230 Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Laszlo Ersek <lersek@redhat.com> Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
2016-11-30 20:06:34 +01:00
);
#endif