Re: [PATCH v11 09/10] arm_ffa: efi: introduce FF-A MM communication

[Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>]

On Tue, Apr 18, 2023 at 07:49:07PM -0600, Simon Glass wrote:

Hi Simon,

> 
> On Wed, 12 Apr 2023 at 03:43, Abdellatif El Khlifi
> <abdellatif.elkhlifi@arm.com> wrote:
> >
> > Add MM communication support using FF-A transport
> >
> > This feature allows accessing MM partitions services through
> > EFI MM communication protocol. MM partitions such as StandAlonneMM
> > or smm-gateway secure partitions which reside in secure world.
> >
> > An MM shared buffer and a door bell event are used to exchange
> > the data.
> >
> > The data is used by EFI services such as GetVariable()/SetVariable()
> > and copied from the communication buffer to the MM shared buffer.
> >
> > The secure partition is notified about availability of data in the
> > MM shared buffer by an FF-A message (door bell).
> >
> > On such event, MM SP can read the data and updates the MM shared
> > buffer with the response data.
> >
> > The response data is copied back to the communication buffer and
> > consumed by the EFI subsystem.
> >
> > MM communication protocol supports FF-A 64-bit direct messaging.
> >
> > Signed-off-by: Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>
> > Signed-off-by: Gowtham Suresh Kumar <gowtham.sureshkumar@arm.com>
> > Cc: Tom Rini <trini@konsulko.com>
> > Cc: Simon Glass <sjg@chromium.org>
> > Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
> > Cc: Jens Wiklander <jens.wiklander@linaro.org>
> >
> > ---
> > Changelog:
> > ===============
> >
> > v11:
> >
> > * rename select_ffa_mm_comms() to select_mm_comms()
> > * improve the logic of MM transport selection in mm_communicate()
> > * addressing nits
> >
> > v10:
> >
> > * use the FF-A driver Uclass operations
> > * use uclass_first_device()
> > * addressing nits
> >
> > v9: align how FF-A is used with FF-A discovery through DM
> >
> > v8:
> >
> > * isolate the compilation choices between FF-A and OP-TEE
> > * update partition_info_get() second argument to be an SP count
> > * pass NULL device pointer to the FF-A bus discovery and operations
> >
> > v7:
> >
> > * set the MM door bell event to use 64-bit direct messaging
> > * issue a compile time error when one of these macros are not found :
> >   FFA_SHARED_MM_BUFFER_SIZE, FFA_SHARED_MM_BUFFER_OFFSET, FFA_SHARED_MM_BUFFER_ADDR
> > * make mm_sp_svc_uuid static
> > * replace EINVAL with ENOMEM in ffa_discover_mm_sp_id() when calloc() fails
> > * improve use of unmap_sysmem() in ffa_mm_communicate()
> >
> > v6:
> >
> > * add FF-A runtime discovery at MM communication level
> > * drop EFI runtime support for FF-A MM communication
> > * revert the changes in include/mm_communication.h for
> >   efi_mm_communicate_header and smm_variable_access structures
> >
> > v4:
> >
> > * use the new FF-A driver interfaces
> > * discover MM partitions at runtime
> > * copy FF-A driver private data to EFI runtime section at
> >   ExitBootServices()
> > * drop use of FFA_ERR_STAT_SUCCESS error code
> > * replace EFI_BUFFER_TOO_SMALL with EFI_OUT_OF_RESOURCES
> >   in ffa_mm_communicate(). No need for efi_memcpy_runtime() anymore
> > * revert the error log in mm_communicate() in case of failure
> > * remove packed attribute from efi_mm_communicate_header and
> >   smm_variable_communicate_header
> >
> > v2:
> >
> > * set default values to 0 for FFA_SHARED_MM_BUFFER_SIZE, FFA_SHARED_MM_BUFFER_ADDR and MM_SP_UUID_DATA and add warnings
> >
> > v1:
> >
> > * introduce FF-A MM communication
> >
> >  include/mm_communication.h        |  13 ++
> >  lib/efi_loader/Kconfig            |  14 +-
> >  lib/efi_loader/efi_variable_tee.c | 312 +++++++++++++++++++++++++++++-
> >  3 files changed, 333 insertions(+), 6 deletions(-)
> >
> > diff --git a/include/mm_communication.h b/include/mm_communication.h
> > index e65fbde60d..f17847583b 100644
> > --- a/include/mm_communication.h
> > +++ b/include/mm_communication.h
> > @@ -6,6 +6,9 @@
> >   *  Copyright (c) 2017, Intel Corporation. All rights reserved.
> >   *  Copyright (C) 2020 Linaro Ltd. <sughosh.ganu@linaro.org>
> >   *  Copyright (C) 2020 Linaro Ltd. <ilias.apalodimas@linaro.org>
> > + *  Copyright 2022-2023 Arm Limited and/or its affiliates <open-source-office@arm.com>
> > + *    Authors:
> > + *      Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>
> >   */
> >
> >  #ifndef _MM_COMMUNICATION_H_
> > @@ -13,6 +16,9 @@
> >
> >  #include <part_efi.h>
> >
> > +/* MM service UUID string (big-endian format). This UUID is  common across all MM SPs */
> > +#define MM_SP_UUID     "33d532ed-e699-0942-c09c-a798d9cd722d"
> > +
> >  /*
> >   * Interface to the pseudo Trusted Application (TA), which provides a
> >   * communication channel with the Standalone MM (Management Mode)
> > @@ -248,4 +254,11 @@ struct smm_variable_var_check_property {
> >         u16                       name[];
> >  };
> >
> > +/* supported MM transports */
> > +enum mm_comms_select {
> > +       MM_COMMS_UNDEFINED,
> > +       MM_COMMS_FFA,
> > +       MM_COMMS_OPTEE
> > +};
> > +
> >  #endif /* _MM_COMMUNICATION_H_ */
> > diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
> > index c5835e6ef6..08a6b84101 100644
> > --- a/lib/efi_loader/Kconfig
> > +++ b/lib/efi_loader/Kconfig
> > @@ -55,13 +55,23 @@ config EFI_VARIABLE_FILE_STORE
> >           stored as file /ubootefi.var on the EFI system partition.
> >
> >  config EFI_MM_COMM_TEE
> > -       bool "UEFI variables storage service via OP-TEE"
> > -       depends on OPTEE
> > +       bool "UEFI variables storage service via the trusted world"
> > +       depends on OPTEE || ARM_FFA_TRANSPORT
> >         help
> > +         Allowing access to the MM SP services (SPs such as  StandAlonneMM, smm-gateway).
> > +         When using the u-boot OP-TEE driver, StandAlonneMM is supported.
> > +         When using the u-boot FF-A  driver any MM SP is supported.
> > +
> >           If OP-TEE is present and running StandAloneMM, dispatch all UEFI
> >           variable related operations to that. The application will verify,
> >           authenticate and store the variables on an RPMB.
> >
> > +         When ARM_FFA_TRANSPORT is used, dispatch all UEFI variable related
> > +         operations to the MM SP running in the secure world.
> > +         A door bell mechanism is used to notify the SP when there is data in the shared
> > +         MM buffer. The data is copied by u-boot to the shared buffer before issuing
> > +         the door bell event.
> > +
> >  config EFI_VARIABLE_NO_STORE
> >         bool "Don't persist non-volatile UEFI variables"
> >         help
> > diff --git a/lib/efi_loader/efi_variable_tee.c b/lib/efi_loader/efi_variable_tee.c
> > index dfef18435d..a6ec126db5 100644
> > --- a/lib/efi_loader/efi_variable_tee.c
> > +++ b/lib/efi_loader/efi_variable_tee.c
> > @@ -4,9 +4,14 @@
> >   *
> >   *  Copyright (C) 2019 Linaro Ltd. <sughosh.ganu@linaro.org>
> >   *  Copyright (C) 2019 Linaro Ltd. <ilias.apalodimas@linaro.org>
> > + *  Copyright 2022-2023 Arm Limited and/or its affiliates <open-source-office@arm.com>
> > + *
> > + *  Authors:
> > + *    Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>
> >   */
> >
> >  #include <common.h>
> > +#include <dm.h>
> >  #include <efi.h>
> >  #include <efi_api.h>
> >  #include <efi_loader.h>
> > @@ -15,6 +20,36 @@
> >  #include <malloc.h>
> >  #include <mm_communication.h>
> >
> > +#if (IS_ENABLED(CONFIG_ARM_FFA_TRANSPORT))
> > +
> > +#include <arm_ffa.h>
> > +#include <cpu_func.h>
> > +#include <mapmem.h>
> > +
> > +#ifndef FFA_SHARED_MM_BUFFER_SIZE
> > +#error "FFA_SHARED_MM_BUFFER_SIZE must be defined in include/configs/<board>.h"
> > +#define FFA_SHARED_MM_BUFFER_SIZE 0
> > +#endif
> > +
> > +#ifndef FFA_SHARED_MM_BUFFER_OFFSET
> > +#error "FFA_SHARED_MM_BUFFER_OFFSET must be defined in include/configs/<board>.h"
> > +#define FFA_SHARED_MM_BUFFER_OFFSET 0
> > +#endif
> > +
> > +#ifndef FFA_SHARED_MM_BUFFER_ADDR
> > +#error "FFA_SHARED_MM_BUFFER_ADDR must be defined in include/configs/<board>.h"
> > +#define FFA_SHARED_MM_BUFFER_ADDR 0
> > +#endif
> > +
> > +/* MM return codes */
> > +#define MM_SUCCESS (0)
> > +
> > +static const char *mm_sp_svc_uuid = MM_SP_UUID;
> > +
> > +static u16 mm_sp_id;
> > +
> > +#endif
> > +
> >  extern struct efi_var_file __efi_runtime_data *efi_var_buf;
> >  static efi_uintn_t max_buffer_size;    /* comm + var + func + data */
> >  static efi_uintn_t max_payload_size;   /* func + data */
> > @@ -24,6 +59,7 @@ struct mm_connection {
> >         u32 session;
> >  };
> >
> > +#if (IS_ENABLED(CONFIG_OPTEE))
> >  /**
> >   * get_connection() - Retrieve OP-TEE session for a specific UUID.
> >   *
> > @@ -60,6 +96,7 @@ static int get_connection(struct mm_connection *conn)
> >  out:
> >         return rc;
> >  }
> > +#endif
> >
> >  /**
> >   * optee_mm_communicate() - Pass a buffer to StandaloneMM running in OP-TEE
> > @@ -70,6 +107,7 @@ out:
> >   */
> >  static efi_status_t optee_mm_communicate(void *comm_buf, ulong dsize)
> >  {
> > +#if (IS_ENABLED(CONFIG_OPTEE))
> >         ulong buf_size;
> >         efi_status_t ret;
> >         struct efi_mm_communicate_header *mm_hdr;
> > @@ -142,19 +180,269 @@ static efi_status_t optee_mm_communicate(void *comm_buf, ulong dsize)
> >         }
> >
> >         return ret;
> > +#else
> > +       log_err("EFI: Please enable CONFIG_OPTEE for MM comms\n");
> > +       return EFI_UNSUPPORTED;
> > +#endif
> > +}
> > +
> > +#if (IS_ENABLED(CONFIG_ARM_FFA_TRANSPORT))
> 
> drop extra brackets
> 
> > +
> > +/**
> > + * ffa_notify_mm_sp() - Announce there is data in the shared buffer
> > + *
> > + * Notify the MM partition in the trusted world that
> > + * data is available in the shared buffer.
> > + * This is a blocking call during which trusted world has exclusive access
> > + * to the MM shared buffer.
> > + *
> > + * Return:
> > + *
> > + * 0 on success
> > + */
> > +static int ffa_notify_mm_sp(void)
> > +{
> > +       struct ffa_send_direct_data msg = {0};
> > +       int ret;
> > +       int sp_event_ret = -1;
> > +       struct udevice *dev;
> > +
> > +       ret = uclass_first_device_err(UCLASS_FFA, &dev);
> > +       if (ret) {
> > +               log_err("EFI: Cannot find FF-A bus device, notify MM SP failure\n");
> > +               return -ENODEV;
> 
> return ret
> 
> > +       }
> > +
> > +       msg.data0 = FFA_SHARED_MM_BUFFER_OFFSET; /* x3 */
> > +
> > +       ret = ffa_sync_send_receive(dev, mm_sp_id, &msg, 1);
> > +       if (ret)
> > +               return ret;
> > +
> > +       sp_event_ret = msg.data0; /* x3 */
> > +
> > +       if (sp_event_ret == MM_SUCCESS)
> > +               return 0;
> > +
> > +       /* Failure to notify the MM SP */
> > +
> > +       return -EACCES;
> > +}
> > +
> > +/**
> > + * ffa_discover_mm_sp_id() - Query the MM partition ID
> > + *
> > + * Use the FF-A driver to get the MM partition ID.
> > + * If multiple partitions are found, use the first one.
> > + * This is a boot time function.
> > + *
> > + * Return:
> > + *
> > + * 0 on success
> > + */
> > +static int ffa_discover_mm_sp_id(void)
> > +{
> > +       u32 count = 0;
> > +       int ret;
> > +       struct ffa_partition_info *parts_info;
> > +       struct udevice *dev;
> > +
> > +       ret = uclass_first_device_err(UCLASS_FFA, &dev);
> > +       if (ret) {
> > +               log_err("EFI: Cannot find FF-A bus device, MM SP discovery failure\n");
> > +               return -ENODEV;
> 
> return ret
> 
> Please check that you don't change error returns unless you really
> want to, as it makes it hard to debug failures.
> 
> > +       }
> > +
> > +       /* Get from the driver the count of the SPs matching the UUID */
> > +       ret = ffa_partition_info_get(dev, mm_sp_svc_uuid, &count, NULL);
> > +       if (ret) {
> > +               log_err("EFI: Failure in querying SPs count (%d), MM SP discovery failure\n", ret);
> > +               return ret;
> > +       }
> > +
> > +       if (!count) {
> > +               log_info("EFI: No MM partition found\n");
> > +               return ret;
> > +       }
> > +
> > +       /* Pre-allocate a buffer to be filled by the driver with ffa_partition_info structs */
> > +
> > +       log_info("EFI: Pre-allocating %d partition(s) info structures\n", count);
> > +
> > +       parts_info = calloc(count, sizeof(*parts_info));
> 
> Use a local var and drop the calloc()
> 
> > +       if (!parts_info)
> > +               return -ENOMEM;
> > +
> > +       /* Ask the driver to fill the buffer with the SPs info */
> > +       ret = ffa_partition_info_get(dev, mm_sp_svc_uuid, &count, parts_info);
> > +       if (ret) {
> > +               log_err("EFI: Failure in querying SPs info (%d), MM SP discovery failure\n", ret);
> > +               free(parts_info);
> > +               return ret;
> > +       }
> > +
> > +       /* MM SPs found , use the first one */
> > +
> > +       mm_sp_id = parts_info[0].id;
> > +
> > +       log_info("EFI: MM partition ID 0x%x\n", mm_sp_id);
> > +
> > +       free(parts_info);
> > +
> > +       return 0;
> > +}
> > +#endif
> > +
> > +/**
> > + * ffa_mm_communicate() - Exchange EFI services data with  the MM partition using FF-A
> > + * @comm_buf:          locally allocated communication buffer used for rx/tx
> > + * @dsize:                             communication buffer size
> > + *
> > + * Issue a door bell event to notify the MM partition (SP) running in OP-TEE
> > + * that there is data to read from the shared buffer.
> > + * Communication with the MM SP is performed using FF-A transport.
> > + * On the event, MM SP can read the data from the buffer and
> > + * update the MM shared buffer with response data.
> > + * The response data is copied back to the communication buffer.
> > + *
> > + * Return:
> > + *
> > + * EFI status code
> > + */
> > +static efi_status_t ffa_mm_communicate(void *comm_buf, ulong comm_buf_size)
> > +{
> > +#if (IS_ENABLED(CONFIG_ARM_FFA_TRANSPORT))
> 
> Please use if() if you can?

Thanks for pointing out this. I'm trying my best to reduce the #ifdefs as much as possible.
For this one, what goes under the #ifdef is specific to FF-A. It doesn't make sense to compile
the FF-A logic and functions when we don't turn on the FF-A config.
I agreed with Ilias to keep ffa_mm_communicate() as a stub in case FF-A is off, and to show a message
at the preprocessor level.

> 
> > +       ulong tx_data_size;
> > +       int ffa_ret;
> > +       efi_status_t efi_ret;
> > +       struct efi_mm_communicate_header *mm_hdr;
> > +       void *virt_shared_buf;
> > +
> > +       if (!comm_buf)
> > +               return EFI_INVALID_PARAMETER;
> > +
> > +       /* Discover MM partition ID at boot time */
> > +       if (!mm_sp_id && ffa_discover_mm_sp_id()) {
> > +               log_err("EFI: Failure to discover MM SP ID at boot time, FF-A MM comms failure\n");
> > +               return EFI_UNSUPPORTED;
> > +       }
> > +
> > +       mm_hdr = (struct efi_mm_communicate_header *)comm_buf;
> > +       tx_data_size = mm_hdr->message_len + sizeof(efi_guid_t) + sizeof(size_t);
> > +
> > +       if (comm_buf_size != tx_data_size || tx_data_size > FFA_SHARED_MM_BUFFER_SIZE)
> > +               return EFI_INVALID_PARAMETER;
> > +
> > +       /* Copy the data to the shared buffer */
> > +
> > +       virt_shared_buf = map_sysmem((phys_addr_t)FFA_SHARED_MM_BUFFER_ADDR, 0);
> > +       memcpy(virt_shared_buf, comm_buf, tx_data_size);
> > +
> > +       /*
> > +        * The secure world might have cache disabled for
> > +        * the device region used for shared buffer (which is the case for Optee).
> > +        * In this case, the secure world reads the data from DRAM.
> > +        * Let's flush the cache so the DRAM is updated with the latest data.
> > +        */
> > +#ifdef CONFIG_ARM64
> > +       invalidate_dcache_all();
> > +#endif
> > +
> > +       /* Announce there is data in the shared buffer */
> > +
> > +       ffa_ret = ffa_notify_mm_sp();
> > +
> > +       switch (ffa_ret) {
> > +       case 0: {
> > +               ulong rx_data_size;
> > +               /* Copy the MM SP response from the shared buffer to the communication buffer */
> > +               rx_data_size = ((struct efi_mm_communicate_header *)virt_shared_buf)->message_len +
> > +                       sizeof(efi_guid_t) +
> > +                       sizeof(size_t);
> > +
> > +               if (rx_data_size > comm_buf_size) {
> > +                       efi_ret = EFI_OUT_OF_RESOURCES;
> > +                       break;
> > +               }
> > +
> > +               memcpy(comm_buf, virt_shared_buf, rx_data_size);
> > +               efi_ret = EFI_SUCCESS;
> > +               break;
> > +       }
> > +       case -EINVAL:
> > +               efi_ret = EFI_DEVICE_ERROR;
> > +               break;
> > +       case -EPERM:
> > +               efi_ret = EFI_INVALID_PARAMETER;
> > +               break;
> > +       case -EACCES:
> > +               efi_ret = EFI_ACCESS_DENIED;
> > +               break;
> > +       case -EBUSY:
> > +               efi_ret = EFI_OUT_OF_RESOURCES;
> > +               break;
> > +       default:
> > +               efi_ret = EFI_ACCESS_DENIED;
> > +       }
> > +
> > +       unmap_sysmem(virt_shared_buf);
> > +       return efi_ret;
> > +#else
> > +       log_err("EFI: Please enable CONFIG_ARM_FFA_TRANSPORT for MM comms\n");
> > +       return EFI_UNSUPPORTED;
> > +#endif
> > +}
> > +
> > +/**
> > + * select_mm_comms() - detect the available MM transport
> > + *
> > + * If FF-A is compiled in, make sure the FF-A bus is probed successfully
> > + * which means FF-A communication with secure world works and ready
> > + * to be used.
> > + *
> > + * If FF-A is not detected, check if OPTEE support is compiled in.
> > + *
> > + * Return:
> > + *
> > + * On success MM_COMMS_FFA or MM_COMMS_OPTEE. Otherwise, MM_COMMS_UNDEFINED
> > + */
> > +static enum mm_comms_select select_mm_comms(void)
> > +{
> > +       struct udevice *dev;
> > +       int ret;
> > +
> > +       if (IS_ENABLED(CONFIG_ARM_FFA_TRANSPORT)) {
> > +               ret = uclass_first_device_err(UCLASS_FFA, &dev);
> > +               if (ret)
> > +                       log_err("EFI: Cannot find FF-A bus device, cannot select FF-A comms\n");
> > +               else
> > +                       return MM_COMMS_FFA;
> > +       }
> > +
> > +       if (IS_ENABLED(CONFIG_OPTEE))
> > +               return MM_COMMS_OPTEE;
> > +
> > +       return MM_COMMS_UNDEFINED;
> >  }
> >
> >  /**
> > - * mm_communicate() - Adjust the cmonnucation buffer to StandAlonneMM and send
> > + * mm_communicate() - Adjust the communication buffer to the MM SP and send
> >   * it to OP-TEE
> >   *
> > - * @comm_buf:          locally allocted communcation buffer
> > + * @comm_buf:          locally allocated communication buffer
> >   * @dsize:             buffer size
> > + *
> > + * The SP (also called partition) can be any MM SP such as  StandAlonneMM or smm-gateway.
> > + * The comm_buf format is the same for both partitions.
> > + * When using the u-boot OP-TEE driver, StandAlonneMM is supported.
> > + * When using the u-boot FF-A  driver, any MM SP is supported.
> > + *
> >   * Return:             status code
> >   */
> >  static efi_status_t mm_communicate(u8 *comm_buf, efi_uintn_t dsize)
> >  {
> >         efi_status_t ret;
> > +       enum mm_comms_select mm_comms;
> >         struct efi_mm_communicate_header *mm_hdr;
> >         struct smm_variable_communicate_header *var_hdr;
> >
> > @@ -162,7 +450,16 @@ static efi_status_t mm_communicate(u8 *comm_buf, efi_uintn_t dsize)
> >         mm_hdr = (struct efi_mm_communicate_header *)comm_buf;
> >         var_hdr = (struct smm_variable_communicate_header *)mm_hdr->data;
> >
> > -       ret = optee_mm_communicate(comm_buf, dsize);
> > +       mm_comms = select_mm_comms();
> > +       if (mm_comms == MM_COMMS_UNDEFINED) {
> > +               ret = EFI_UNSUPPORTED;
> > +       } else {
> > +               if (mm_comms == MM_COMMS_OPTEE)
> > +                       ret = optee_mm_communicate(comm_buf, dsize);
> > +               else
> > +                       ret = ffa_mm_communicate(comm_buf, dsize);
> > +       }
> > +
> >         if (ret != EFI_SUCCESS) {
> >                 log_err("%s failed!\n", __func__);
> >                 return ret;
> > @@ -258,6 +555,13 @@ efi_status_t EFIAPI get_max_payload(efi_uintn_t *size)
> >                 goto out;
> >         }
> >         *size = var_payload->size;
> > +
> > +       #if (IS_ENABLED(CONFIG_ARM_FFA_TRANSPORT))
> 
> Can this use if () ?

FFA_SHARED_MM_BUFFER_SIZE is a platform-specific value related to the MM layer (firmware).
Platforms that don't use FF-A won't define FFA_SHARED_MM_BUFFER_SIZE, leading to a compilation error.
So, we need to use an #ifdef in this case.

Cheers,
Abdellatif

> 
> > +               if (*size > FFA_SHARED_MM_BUFFER_SIZE)
> > +                       *size = FFA_SHARED_MM_BUFFER_SIZE - MM_COMMUNICATE_HEADER_SIZE  -
> > +                               MM_VARIABLE_COMMUNICATE_SIZE;
> > +       #endif
> > +
> >         /*
> >          * There seems to be a bug in EDK2 miscalculating the boundaries and
> >          * size checks, so deduct 2 more bytes to fulfill this requirement. Fix
> > @@ -697,7 +1001,7 @@ void efi_variables_boot_exit_notify(void)
> >                 ret = EFI_NOT_FOUND;
> >
> >         if (ret != EFI_SUCCESS)
> > -               log_err("Unable to notify StMM for ExitBootServices\n");
> > +               log_err("Unable to notify the MM partition for ExitBootServices\n");
> >         free(comm_buf);
> >
> >         /*
> > --
> > 2.25.1
> >
> 
> Regards,
> Simon