Re: [PATCH 04/12] xen/arm: ffa: Add FF-A 1.2 endpoint memory access descriptors

[Jens Wiklander <jens.wiklander@xxxxxxxxxx>]

Hi Bertrand,

On Tue, Feb 3, 2026 at 6:38 PM Bertrand Marquis
<bertrand.marquis@xxxxxxx> wrote:
>
> FF-A 1.2 extends the endpoint memory access descriptor (EMAD) from
> 16 to 32 bytes, adding implementation-defined (IMPDEF) fields and
> reserved space. The MEM_SHARE path currently assumes the 1.1 EMAD
> size and rejects the 1.2 layout.
>
> Add FF-A 1.2 EMAD support to MEM_SHARE:
> - define ffa_mem_access_1_2 and store IMPDEF payload in ffa_shm_mem
> - emit 1.2 EMADs to the SPMC for FF-A 1.2 guests, forwarding IMPDEF
> - refactor header parsing into read_mem_transaction() for 1.0/1.1+
> - detect EMAD format by mem_access_size to allow 1.1 on 1.2 guests
>
> Functional impact: MEM_SHARE supports FF-A 1.2 EMADs.
>
> Signed-off-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
> ---
>  xen/arch/arm/tee/ffa_shm.c | 108 +++++++++++++++++++++++++++++--------
>  1 file changed, 86 insertions(+), 22 deletions(-)
>
> diff --git a/xen/arch/arm/tee/ffa_shm.c b/xen/arch/arm/tee/ffa_shm.c
> index 4c0b45cde6ee..905a64e3db01 100644
> --- a/xen/arch/arm/tee/ffa_shm.c
> +++ b/xen/arch/arm/tee/ffa_shm.c
> @@ -30,6 +30,14 @@ struct ffa_mem_access {
>      uint64_t reserved;
>  };
>
> +/* Endpoint memory access descriptor (FF-A 1.2) */
> +struct ffa_mem_access_1_2 {
> +    struct ffa_mem_access_perm access_perm;
> +    uint32_t region_offs;
> +    uint8_t impdef[16];
> +    uint8_t reserved[8];
> +};
> +
>  /* Lend, donate or share memory transaction descriptor */
>  struct ffa_mem_transaction_1_0 {
>      uint16_t sender_id;
> @@ -73,7 +81,7 @@ struct ffa_mem_transaction_1_1 {
>  /*
>   * The parts needed from struct ffa_mem_transaction_1_0 or struct
>   * ffa_mem_transaction_1_1, used to provide an abstraction of difference in
> - * data structures between version 1.0 and 1.1. This is just an internal
> + * data structures between version 1.0 and 1.2. This is just an internal
>   * interface and can be changed without changing any ABI.
>   */
>  struct ffa_mem_transaction_int {
> @@ -92,6 +100,8 @@ struct ffa_shm_mem {
>      uint16_t sender_id;
>      uint16_t ep_id;     /* endpoint, the one lending */
>      uint64_t handle;    /* FFA_HANDLE_INVALID if not set yet */
> +    /* Endpoint memory access descriptor IMPDEF value (FF-A 1.2). */
> +    uint64_t impdef[2];
>      unsigned int page_count;
>      struct page_info *pages[];
>  };
> @@ -297,17 +307,21 @@ static void init_range(struct ffa_address_range 
> *addr_range,
>   * This function uses the ffa_spmc tx buffer to transmit the memory 
> transaction
>   * descriptor.
>   */
> -static int share_shm(struct ffa_shm_mem *shm)
> +static int share_shm(struct ffa_shm_mem *shm, uint32_t ffa_vers)
>  {
>      const uint32_t max_frag_len = FFA_RXTX_PAGE_COUNT * FFA_PAGE_SIZE;
>      struct ffa_mem_access *mem_access_array;
> +    struct ffa_mem_access_1_2 *mem_access_array_1_2;
>      struct ffa_mem_transaction_1_1 *descr;
>      struct ffa_address_range *addr_range;
>      struct ffa_mem_region *region_descr;
> -    const unsigned int region_count = 1;
>      uint32_t frag_len;
>      uint32_t tot_len;
> +    uint32_t mem_access_size;
> +    uint32_t mem_access_offs;
> +    uint32_t region_offs;
>      paddr_t last_pa;
> +    uint32_t range_count;
>      unsigned int n;
>      paddr_t pa;
>      int32_t ret;
> @@ -326,16 +340,35 @@ static int share_shm(struct ffa_shm_mem *shm)
>      descr->handle = shm->handle;
>      descr->mem_reg_attr = FFA_NORMAL_MEM_REG_ATTR;
>      descr->mem_access_count = 1;
> -    descr->mem_access_size = sizeof(*mem_access_array);
> -    descr->mem_access_offs = MEM_ACCESS_OFFSET(0);
> +    if ( ffa_vers >= FFA_VERSION_1_2 )
> +        mem_access_size = sizeof(struct ffa_mem_access_1_2);
> +    else
> +        mem_access_size = sizeof(struct ffa_mem_access);
> +    mem_access_offs = sizeof(struct ffa_mem_transaction_1_1);
> +    region_offs = mem_access_offs + mem_access_size;
> +    descr->mem_access_size = mem_access_size;
> +    descr->mem_access_offs = mem_access_offs;
>
> -    mem_access_array = buf + descr->mem_access_offs;
> -    memset(mem_access_array, 0, sizeof(*mem_access_array));
> -    mem_access_array[0].access_perm.endpoint_id = shm->ep_id;
> -    mem_access_array[0].access_perm.perm = FFA_MEM_ACC_RW;
> -    mem_access_array[0].region_offs = REGION_OFFSET(descr->mem_access_count, 
> 0);
> +    if ( ffa_vers >= FFA_VERSION_1_2 )
> +    {
> +        mem_access_array_1_2 = buf + mem_access_offs;
> +        memset(mem_access_array_1_2, 0, sizeof(*mem_access_array_1_2));
> +        mem_access_array_1_2[0].access_perm.endpoint_id = shm->ep_id;
> +        mem_access_array_1_2[0].access_perm.perm = FFA_MEM_ACC_RW;
> +        mem_access_array_1_2[0].region_offs = region_offs;
> +        memcpy(mem_access_array_1_2[0].impdef, shm->impdef,
> +               sizeof(mem_access_array_1_2[0].impdef));
> +    }
> +    else
> +    {
> +        mem_access_array = buf + mem_access_offs;
> +        memset(mem_access_array, 0, sizeof(*mem_access_array));
> +        mem_access_array[0].access_perm.endpoint_id = shm->ep_id;
> +        mem_access_array[0].access_perm.perm = FFA_MEM_ACC_RW;
> +        mem_access_array[0].region_offs = region_offs;
> +    }
>
> -    region_descr = buf + mem_access_array[0].region_offs;
> +    region_descr = buf + region_offs;
>      memset(region_descr, 0, sizeof(*region_descr));
>      region_descr->total_page_count = shm->page_count;
>
> @@ -349,8 +382,9 @@ static int share_shm(struct ffa_shm_mem *shm)
>          region_descr->address_range_count++;
>      }
>
> -    tot_len = ADDR_RANGE_OFFSET(descr->mem_access_count, region_count,
> -                                region_descr->address_range_count);

Please remove the unused ADDR_RANGE_OFFSET() macro and friends, as
they're no longer accurate.

> +    range_count = region_descr->address_range_count;
> +    tot_len = region_offs + sizeof(*region_descr) +
> +              range_count * sizeof(struct ffa_address_range);
>      if ( tot_len > max_frag_len )
>      {
>          ret = FFA_RET_NOT_SUPPORTED;
> @@ -358,7 +392,7 @@ static int share_shm(struct ffa_shm_mem *shm)
>      }
>
>      addr_range = region_descr->address_range_array;
> -    frag_len = ADDR_RANGE_OFFSET(descr->mem_access_count, region_count, 1);
> +    frag_len = region_offs + sizeof(*region_descr) + sizeof(*addr_range);
>      last_pa = page_to_maddr(shm->pages[0]);
>      init_range(addr_range, last_pa);
>      for ( n = 1; n < shm->page_count; last_pa = pa, n++ )
> @@ -448,6 +482,12 @@ static int read_mem_transaction(uint32_t ffa_vers, const 
> void *buf, size_t blen,
>      if ( size * count + offs > blen )
>          return FFA_RET_INVALID_PARAMETERS;
>
> +    if ( size < sizeof(struct ffa_mem_access) )
> +        return FFA_RET_INVALID_PARAMETERS;

Implicitly, size should also be a multiple of 16. Don't you agree?

> +
> +    if ( offs & 0xF )
> +        return FFA_RET_INVALID_PARAMETERS;
> +
>      trans->mem_reg_attr = mem_reg_attr;
>      trans->flags = flags;
>      trans->mem_access_size = size;
> @@ -464,7 +504,7 @@ void ffa_handle_mem_share(struct cpu_user_regs *regs)
>      uint64_t addr = get_user_reg(regs, 3);
>      uint32_t page_count = get_user_reg(regs, 4);
>      const struct ffa_mem_region *region_descr;
> -    const struct ffa_mem_access *mem_access;
> +    const struct ffa_mem_access_1_2 *mem_access;
>      struct ffa_mem_transaction_int trans;
>      struct domain *d = current->domain;
>      struct ffa_ctx *ctx = d->arch.tee;
> @@ -474,9 +514,12 @@ void ffa_handle_mem_share(struct cpu_user_regs *regs)
>      register_t handle_hi = 0;
>      register_t handle_lo = 0;
>      int ret = FFA_RET_DENIED;
> +    uint32_t ffa_vers;
>      uint32_t range_count;
>      uint32_t region_offs;
>      uint16_t dst_id;
> +    uint8_t perm;
> +    uint64_t impdef[2];
>
>      if ( !ffa_fw_supports_fid(FFA_MEM_SHARE_64) )
>      {
> @@ -515,8 +558,8 @@ void ffa_handle_mem_share(struct cpu_user_regs *regs)
>      if ( frag_len > tx_size )
>          goto out_unlock;
>
> -    ret = read_mem_transaction(ACCESS_ONCE(ctx->guest_vers), tx_buf,
> -                               frag_len, &trans);
> +    ffa_vers = ACCESS_ONCE(ctx->guest_vers);
> +    ret = read_mem_transaction(ffa_vers, tx_buf, frag_len, &trans);
>      if ( ret )
>          goto out_unlock;
>
> @@ -545,13 +588,35 @@ void ffa_handle_mem_share(struct cpu_user_regs *regs)
>          goto out_unlock;
>      }
>
> +    if ( trans.mem_access_size < sizeof(struct ffa_mem_access) )
> +    {
> +        ret = FFA_RET_INVALID_PARAMETERS;
> +        goto out_unlock;
> +    }
> +
>      /* Check that it fits in the supplied data */
>      if ( trans.mem_access_offs + trans.mem_access_size > frag_len )
>          goto out_unlock;
>
>      mem_access = tx_buf + trans.mem_access_offs;
> -
>      dst_id = ACCESS_ONCE(mem_access->access_perm.endpoint_id);
> +    perm = ACCESS_ONCE(mem_access->access_perm.perm);
> +    region_offs = ACCESS_ONCE(mem_access->region_offs);
> +
> +    /*
> +     * FF-A 1.2 introduced an extended mem_access descriptor with impdef
> +     * fields, but guests can still use the 1.1 format if they don't need
> +     * implementation-defined data. Detect which format is used based on
> +     * the mem_access_size field rather than the negotiated FF-A version.
> +     */
> +    if ( trans.mem_access_size >= sizeof(struct ffa_mem_access_1_2) )
> +        memcpy(impdef, mem_access->impdef, sizeof(impdef));
> +    else
> +    {
> +        impdef[0] = 0;
> +        impdef[1] = 0;
> +    }
> +
>      if ( !FFA_ID_IS_SECURE(dst_id) )
>      {
>          /* we do not support sharing with VMs */
> @@ -559,13 +624,11 @@ void ffa_handle_mem_share(struct cpu_user_regs *regs)
>          goto out_unlock;
>      }
>
> -    if ( ACCESS_ONCE(mem_access->access_perm.perm) != FFA_MEM_ACC_RW )
> +    if ( perm != FFA_MEM_ACC_RW )
>      {
>          ret = FFA_RET_NOT_SUPPORTED;
>          goto out_unlock;
>      }
> -
> -    region_offs = ACCESS_ONCE(mem_access->region_offs);
>      if ( sizeof(*region_descr) + region_offs > frag_len )
>      {
>          ret = FFA_RET_NOT_SUPPORTED;
> @@ -590,6 +653,7 @@ void ffa_handle_mem_share(struct cpu_user_regs *regs)
>      }
>      shm->sender_id = trans.sender_id;
>      shm->ep_id = dst_id;
> +    memcpy(shm->impdef, impdef, sizeof(shm->impdef));
>
>      /*
>       * Check that the Composite memory region descriptor fits.
> @@ -605,7 +669,7 @@ void ffa_handle_mem_share(struct cpu_user_regs *regs)
>      if ( ret )
>          goto out;
>
> -    ret = share_shm(shm);
> +    ret = share_shm(shm, ffa_vers);

Shouldn't we rather use ffa_fw_version?

Cheers,
Jens

>      if ( ret )
>          goto out;
>
> --
> 2.50.1 (Apple Git-155)
>