Re: [PATCH v2 08/16] OvmfPkg/CpuHotplugSmm: define the QEMU_CPUHP_CMD_GET_ARCH_ID macro

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 2/26/20 11:11 PM, Laszlo Ersek wrote:
> QEMU commit 3a61c8db9d25 ("acpi: cpuhp: add CPHP_GET_CPU_ID_CMD command",
> 2020-01-22) introduced a new command in the modern CPU hotplug register
> block that lets the firmware query the arch-specific IDs (on IA32/X64: the
> APIC IDs) of CPUs. Add a macro for this command value, because we'll need
> it later.
> 
> At the same time, add a sanity check for the modern hotplug interface to
> CpuHotplugSmm.
> 
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Michael Kinney <michael.d.kinney@intel.com>
> Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1512
> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
> Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
> 
> Notes:
>      v2:
>      
>      - Pick up Ard's Acked-by, which is conditional on approval from Intel
>        reviewers on Cc. (I'd like to save Ard the churn of re-acking
>        unmodified patches.)
> 
>   OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h |  1 +
>   OvmfPkg/CpuHotplugSmm/CpuHotplug.c                | 35 ++++++++++++++++++++
>   2 files changed, 36 insertions(+)
> 
> diff --git a/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h b/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h
> index cf0745610f2c..3d013633501b 100644
> --- a/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h
> +++ b/OvmfPkg/Include/IndustryStandard/QemuCpuHotplug.h
> @@ -20,24 +20,25 @@
>   #define QEMU_CPU_HOTPLUG_H_
>   
>   #include <Base.h>
>   
>   //
>   // Each register offset is:
>   // - relative to the board-dependent IO base address of the register block,
>   // - named QEMU_CPUHP_(R|W|RW)_*, according to the possible access modes of the
>   //   register,
>   // - followed by distinguished bitmasks or values in the register.
>   //
>   #define QEMU_CPUHP_R_CMD_DATA2               0x0
>   
>   #define QEMU_CPUHP_R_CPU_STAT                0x4
>   #define QEMU_CPUHP_STAT_ENABLED                BIT0
>   
>   #define QEMU_CPUHP_RW_CMD_DATA               0x8
>   
>   #define QEMU_CPUHP_W_CPU_SEL                 0x0
>   
>   #define QEMU_CPUHP_W_CMD                     0x5
>   #define QEMU_CPUHP_CMD_GET_PENDING             0x0
> +#define QEMU_CPUHP_CMD_GET_ARCH_ID             0x3
>   
>   #endif // QEMU_CPU_HOTPLUG_H_
> diff --git a/OvmfPkg/CpuHotplugSmm/CpuHotplug.c b/OvmfPkg/CpuHotplugSmm/CpuHotplug.c
> index fd09403eabf3..5df8c689c63a 100644
> --- a/OvmfPkg/CpuHotplugSmm/CpuHotplug.c
> +++ b/OvmfPkg/CpuHotplugSmm/CpuHotplug.c
> @@ -1,38 +1,41 @@
>   /** @file
>     Root SMI handler for VCPU hotplug SMIs.
>   
>     Copyright (c) 2020, Red Hat, Inc.
>   
>     SPDX-License-Identifier: BSD-2-Clause-Patent
>   **/
>   
>   #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 <Protocol/MmCpuIo.h>                // EFI_MM_CPU_IO_PROTOCOL
>   #include <Uefi/UefiBaseType.h>               // EFI_STATUS
>   
> +#include "QemuCpuhp.h"                       // QemuCpuhpWriteCpuSelector()
> +
>   //
>   // We use this protocol for accessing IO Ports.
>   //
>   STATIC EFI_MM_CPU_IO_PROTOCOL *mMmCpuIo;
>   //
>   // 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.
> @@ -149,43 +152,75 @@ CpuHotplugEntry (
>     //
>     // 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;
>     }
>   
> +  //
> +  // 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);

Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>

> +  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 Fatal;
> +  }
> +
>     //
>     // 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 Fatal;
>     }
>   
>     return EFI_SUCCESS;
>   
>   Fatal:
>     ASSERT (FALSE);
>     CpuDeadLoop ();
>     return Status;
>   }
>