Re: [PATCH v1 1/1] OvmfPkg/PlatformPei: clear CPU caches

["Kinney, Michael D" <michael.d.kinney@intel.com>]

Hi,

Could you use a service from the CacheMaintenanceLib instead?

/**
  Writes back and invalidates the entire data cache in cache coherency domain
  of the calling CPU.

  Writes back and invalidates the entire data cache in cache coherency domain
  of the calling CPU. This function guarantees that all dirty cache lines are
  written back to system memory, and also invalidates all the data cache lines
  in the cache coherency domain of the calling CPU.

**/
VOID
EFIAPI
WriteBackInvalidateDataCache (
  VOID
  )

Thanks,

Mike

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-
> bounces@lists.01.org] On Behalf Of
> marcandre.lureau@redhat.com
> Sent: Monday, October 1, 2018 4:45 AM
> To: edk2-devel@lists.01.org
> Cc: Justen, Jordan L <jordan.l.justen@intel.com>;
> Anthony Perard <anthony.perard@citrix.com>; Laszlo
> Ersek <lersek@redhat.com>
> Subject: [edk2] [PATCH v1 1/1] OvmfPkg/PlatformPei:
> clear CPU caches
> 
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> The TCG "Platform Reset Attack Mitigation
> Specification" requires to
> clear the processor caches when the MOR bit is set at
> boot time.
> 
> According to Paolo Bonzini, clearing the CPU cache
> takes only a few
> hundred clock cycles, so it can be done
> unconditionally.
> 
> Flush the cache on all logical processors, thanks to
> EFI_PEI_MP_SERVICES_PPI, calling WBINVD "Write Back and
> Invalidate
> Cache" x86 instruction.
> 
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Anthony Perard <anthony.perard@citrix.com>
> Cc: Julien Grall <julien.grall@linaro.org>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Marc-André Lureau
> <marcandre.lureau@redhat.com>
> ---
>  OvmfPkg/PlatformPei/PlatformPei.inf |   1 +
>  OvmfPkg/PlatformPei/Platform.h      |   5 +
>  OvmfPkg/PlatformPei/ClearCache.c    | 110
> ++++++++++++++++++++
>  OvmfPkg/PlatformPei/Platform.c      |   1 +
>  4 files changed, 117 insertions(+)
> 
> diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf
> b/OvmfPkg/PlatformPei/PlatformPei.inf
> index 9c5ad9961c4a..9c9a95fb3fe5 100644
> --- a/OvmfPkg/PlatformPei/PlatformPei.inf
> +++ b/OvmfPkg/PlatformPei/PlatformPei.inf
> @@ -30,6 +30,7 @@
> 
>  [Sources]
>    AmdSev.c
> +  ClearCache.c
>    Cmos.c
>    Cmos.h
>    FeatureControl.c
> diff --git a/OvmfPkg/PlatformPei/Platform.h
> b/OvmfPkg/PlatformPei/Platform.h
> index f942e61bb4f9..b12a5c1f5f78 100644
> --- a/OvmfPkg/PlatformPei/Platform.h
> +++ b/OvmfPkg/PlatformPei/Platform.h
> @@ -83,6 +83,11 @@ InstallFeatureControlCallback (
>    VOID
>    );
> 
> +VOID
> +InstallClearCacheCallback (
> +  VOID
> +  );
> +
>  EFI_STATUS
>  InitializeXen (
>    VOID
> diff --git a/OvmfPkg/PlatformPei/ClearCache.c
> b/OvmfPkg/PlatformPei/ClearCache.c
> new file mode 100644
> index 000000000000..a1fff8446d13
> --- /dev/null
> +++ b/OvmfPkg/PlatformPei/ClearCache.c
> @@ -0,0 +1,110 @@
> +/**@file
> +  Install a callback to clear cache on all processors.
> +
> +  Copyright (C) 2018, Red Hat, Inc.
> +
> +  This program and the accompanying materials are
> licensed and made available
> +  under the terms and conditions of the BSD License
> which accompanies this
> +  distribution.  The full text of the license may be
> found at
> +  http://opensource.org/licenses/bsd-license.php
> +
> +  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON
> AN "AS IS" BASIS, WITHOUT
> +  WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER
> EXPRESS OR IMPLIED.
> +**/
> +
> +#include <Library/DebugLib.h>
> +#include <Library/PeiServicesLib.h>
> +#include <Ppi/MpServices.h>
> +
> +#include "Platform.h"
> +
> +/**
> +  All APs execute this function in parallel. The BSP
> executes the function
> +  separately.
> +
> +  @param[in,out] WorkSpace  Pointer to the
> input/output argument workspace
> +                            shared by all processors.
> +**/
> +STATIC
> +VOID
> +EFIAPI
> +ClearCache (
> +  IN OUT VOID *WorkSpace
> +  )
> +{
> +  AsmWbinvd ();
> +}
> +
> +/**
> +  Notification function called when
> EFI_PEI_MP_SERVICES_PPI becomes available.
> +
> +  @param[in] PeiServices      Indirect reference to
> the PEI Services Table.
> +  @param[in] NotifyDescriptor Address of the
> notification descriptor data
> +                              structure.
> +  @param[in] Ppi              Address of the PPI that
> was installed.
> +
> +  @return  Status of the notification. The status code
> returned from this
> +           function is ignored.
> +**/
> +STATIC
> +EFI_STATUS
> +EFIAPI
> +OnMpServicesAvailable (
> +  IN EFI_PEI_SERVICES           **PeiServices,
> +  IN EFI_PEI_NOTIFY_DESCRIPTOR  *NotifyDescriptor,
> +  IN VOID                       *Ppi
> +  )
> +{
> +  EFI_PEI_MP_SERVICES_PPI *MpServices;
> +  EFI_STATUS              Status;
> +
> +  DEBUG ((DEBUG_INFO, "%a: %a\n", gEfiCallerBaseName,
> __FUNCTION__));
> +
> +  //
> +  // Clear cache on all the APs in parallel.
> +  //
> +  MpServices = Ppi;
> +  Status = MpServices->StartupAllAPs (
> +                         (CONST EFI_PEI_SERVICES
> **)PeiServices,
> +                         MpServices,
> +                         ClearCache,          //
> Procedure
> +                         FALSE,               //
> SingleThread
> +                         0,                   //
> TimeoutInMicroSeconds: inf.
> +                         NULL                 //
> ProcedureArgument
> +                         );
> +  if (EFI_ERROR (Status) && Status != EFI_NOT_STARTED)
> {
> +    DEBUG ((DEBUG_ERROR, "%a: StartupAllAps(): %r\n",
> __FUNCTION__, Status));
> +    return Status;
> +  }
> +
> +  //
> +  // Now clear cache on the BSP too.
> +  //
> +  ClearCache (NULL);
> +  return EFI_SUCCESS;
> +}
> +
> +//
> +// Notification object for registering the callback,
> for when
> +// EFI_PEI_MP_SERVICES_PPI becomes available.
> +//
> +STATIC CONST EFI_PEI_NOTIFY_DESCRIPTOR
> mMpServicesNotify = {
> +  EFI_PEI_PPI_DESCRIPTOR_NOTIFY_CALLBACK | // Flags
> +  EFI_PEI_PPI_DESCRIPTOR_TERMINATE_LIST,
> +  &gEfiPeiMpServicesPpiGuid,               // Guid
> +  OnMpServicesAvailable                    // Notify
> +};
> +
> +VOID
> +InstallClearCacheCallback (
> +  VOID
> +  )
> +{
> +  EFI_STATUS           Status;
> +
> +  Status = PeiServicesNotifyPpi (&mMpServicesNotify);
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((DEBUG_ERROR, "%a: failed to set up MP
> Services callback: %r\n",
> +      __FUNCTION__, Status));
> +  }
> +}
> diff --git a/OvmfPkg/PlatformPei/Platform.c
> b/OvmfPkg/PlatformPei/Platform.c
> index 5a78668126b4..22139a64cbf4 100644
> --- a/OvmfPkg/PlatformPei/Platform.c
> +++ b/OvmfPkg/PlatformPei/Platform.c
> @@ -672,6 +672,7 @@ InitializePlatform (
>      NoexecDxeInitialization ();
>    }
> 
> +  InstallClearCacheCallback ();
>    AmdSevInitialize ();
>    MiscInitialization ();
>    InstallFeatureControlCallback ();
> --
> 2.19.0.271.gfe8321ec05
> 
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