Re: [PATCH v2 12/12] xen/arm: ffa: Add message parameter diagnostics

[Jens Wiklander <jens.wiklander@xxxxxxxxxx>]

Hi Bertrand,

On Wed, Feb 11, 2026 at 6:16 PM Bertrand Marquis
<bertrand.marquis@xxxxxxx> wrote:
>
> MSG_SEND2 and direct request validation failures are silent, making it
> hard to diagnose invalid IDs, oversized messages, or unsupported
> destination types.
>
> Add debug logs for parameter validation failures:
> - invalid endpoint IDs
> - oversized messages
> - unsupported destination types
> - invalid sender/receiver combinations
> - ratelimit MSG_SEND2 busy failures to avoid log flooding
>
> No functional changes.
>
> Signed-off-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
> ---
> Changes since v1:
> - add a comment to explain ratelimit for BUSY in send2
> ---
>  xen/arch/arm/tee/ffa_msg.c | 49 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)

Looks good:
Reviewed-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>

Cheers,
Jens

>
> diff --git a/xen/arch/arm/tee/ffa_msg.c b/xen/arch/arm/tee/ffa_msg.c
> index 928f269f6c3a..1eadc62870f2 100644
> --- a/xen/arch/arm/tee/ffa_msg.c
> +++ b/xen/arch/arm/tee/ffa_msg.c
> @@ -4,6 +4,7 @@
>   */
>
>  #include <xen/const.h>
> +#include <xen/lib.h>
>  #include <xen/sizes.h>
>  #include <xen/types.h>
>
> @@ -100,6 +101,7 @@ void ffa_handle_msg_send_direct_req(struct cpu_user_regs 
> *regs, uint32_t fid)
>      if ( !ffa_fw_supports_fid(fid) )
>      {
>          ret = FFA_RET_NOT_SUPPORTED;
> +        gdprintk(XENLOG_DEBUG, "ffa: direct req fid %#x not supported\n", 
> fid);
>          goto out;
>      }
>
> @@ -108,6 +110,9 @@ void ffa_handle_msg_send_direct_req(struct cpu_user_regs 
> *regs, uint32_t fid)
>           (src_dst & GENMASK(15,0)) == ffa_get_vm_id(d) )
>      {
>          ret = FFA_RET_INVALID_PARAMETERS;
> +        gdprintk(XENLOG_DEBUG,
> +                 "ffa: direct req invalid src/dst %#x\n",
> +                 (uint32_t)src_dst);
>          goto out;
>      }
>
> @@ -115,6 +120,9 @@ void ffa_handle_msg_send_direct_req(struct cpu_user_regs 
> *regs, uint32_t fid)
>      if ( !FFA_ID_IS_SECURE(src_dst & GENMASK(15,0)) )
>      {
>          ret = FFA_RET_NOT_SUPPORTED;
> +        gdprintk(XENLOG_DEBUG,
> +                 "ffa: direct req to non-secure dst %#x\n",
> +                 (uint32_t)(src_dst & GENMASK(15, 0)));
>          goto out;
>      }
>
> @@ -166,7 +174,12 @@ static int32_t ffa_msg_send2_vm(uint16_t dst_id, const 
> void *src_buf,
>      /* This is also checking that dest is not src */
>      ret = ffa_endpoint_domain_lookup(dst_id, &dst_d, &dst_ctx);
>      if ( ret )
> +    {
> +        gdprintk(XENLOG_DEBUG,
> +                 "ffa: msg_send2 lookup failed: dst %#x ret %d\n",
> +                 dst_id, ret);
>          return ret;
> +    }
>
>      /* This also checks that destination has set a Rx buffer */
>      ret = ffa_rx_acquire(dst_ctx , &rx_buf, &rx_size);
> @@ -199,6 +212,16 @@ static int32_t ffa_msg_send2_vm(uint16_t dst_id, const 
> void *src_buf,
>      /* receiver rx buffer will be released by the receiver*/
>
>  out_unlock:
> +    if ( ret )
> +    {
> +        /**
> +         * Always print other errors than BUSY but ratelimit BUSY prints
> +         * to prevent large number of prints when sender retries on BUSY.
> +         */
> +        if ( ret != FFA_RET_BUSY || printk_ratelimit() )
> +            gdprintk(XENLOG_DEBUG, "ffa: msg_send2 to %#x failed: %d\n",
> +                     dst_id, ret);
> +    }
>      rcu_unlock_domain(dst_d);
>      if ( !ret )
>          ffa_raise_rx_buffer_full(dst_d);
> @@ -226,7 +249,11 @@ int32_t ffa_handle_msg_send2(struct cpu_user_regs *regs)
>
>      ret = ffa_tx_acquire(src_ctx, &tx_buf, &tx_size);
>      if ( ret != FFA_RET_OK )
> +    {
> +        gdprintk(XENLOG_DEBUG,
> +                 "ffa: msg_send2 TX acquire failed: %d\n", ret);
>          return ret;
> +    }
>
>      /* create a copy of the message header */
>      memcpy(&src_msg, tx_buf, sizeof(src_msg));
> @@ -238,6 +265,9 @@ int32_t ffa_handle_msg_send2(struct cpu_user_regs *regs)
>           dst_id == ffa_get_vm_id(src_d) )
>      {
>          ret = FFA_RET_INVALID_PARAMETERS;
> +        gdprintk(XENLOG_DEBUG,
> +                 "ffa: msg_send2 invalid src/dst src %#x dst %#x\n",
> +                 src_id, dst_id);
>          goto out;
>      }
>
> @@ -246,6 +276,9 @@ int32_t ffa_handle_msg_send2(struct cpu_user_regs *regs)
>          if (src_msg.msg_offset < sizeof(struct ffa_part_msg_rxtx_1_1))
>          {
>              ret = FFA_RET_INVALID_PARAMETERS;
> +            gdprintk(XENLOG_DEBUG,
> +                     "ffa: msg_send2 invalid msg_offset %u (v1.1)\n",
> +                     src_msg.msg_offset);
>              goto out;
>          }
>          /* Set uuid to Nil UUID for v1.1 guests */
> @@ -255,6 +288,9 @@ int32_t ffa_handle_msg_send2(struct cpu_user_regs *regs)
>      else if ( src_msg.msg_offset < sizeof(struct ffa_part_msg_rxtx_1_2) )
>      {
>          ret = FFA_RET_INVALID_PARAMETERS;
> +        gdprintk(XENLOG_DEBUG,
> +                 "ffa: msg_send2 invalid msg_offset %u (v1.2)\n",
> +                 src_msg.msg_offset);
>          goto out;
>      }
>
> @@ -263,6 +299,9 @@ int32_t ffa_handle_msg_send2(struct cpu_user_regs *regs)
>              src_msg.msg_size > (tx_size - src_msg.msg_offset) )
>      {
>          ret = FFA_RET_INVALID_PARAMETERS;
> +        gdprintk(XENLOG_DEBUG,
> +                 "ffa: msg_send2 invalid msg_size %u offset %u tx %zu\n",
> +                 src_msg.msg_size, src_msg.msg_offset, tx_size);
>          goto out;
>      }
>
> @@ -272,6 +311,8 @@ int32_t ffa_handle_msg_send2(struct cpu_user_regs *regs)
>          if ( !ffa_fw_supports_fid(FFA_MSG_SEND2) )
>          {
>              ret = FFA_RET_NOT_SUPPORTED;
> +            gdprintk(XENLOG_DEBUG,
> +                     "ffa: msg_send2 to SP not supported\n");
>              goto out;
>          }
>          /*
> @@ -288,6 +329,8 @@ int32_t ffa_handle_msg_send2(struct cpu_user_regs *regs)
>
>          ret = ffa_simple_call(FFA_MSG_SEND2,
>                                ((uint32_t)ffa_get_vm_id(src_d)) << 16, 0, 0, 
> 0);
> +        if ( ret )
> +            gdprintk(XENLOG_DEBUG, "ffa: msg_send2 to SP failed: %d\n", ret);
>      }
>      else if ( IS_ENABLED(CONFIG_FFA_VM_TO_VM) )
>      {
> @@ -295,7 +338,11 @@ int32_t ffa_handle_msg_send2(struct cpu_user_regs *regs)
>          ret = ffa_msg_send2_vm(dst_id, tx_buf, &src_msg);
>      }
>      else
> +    {
>          ret = FFA_RET_INVALID_PARAMETERS;
> +        gdprintk(XENLOG_DEBUG,
> +                 "ffa: msg_send2 to VM disabled (dst %#x)\n", dst_id);
> +    }
>
>  out:
>      ffa_tx_release(src_ctx);
> @@ -311,6 +358,7 @@ void ffa_handle_run(struct cpu_user_regs *regs, uint32_t 
> fid)
>      if ( !ffa_fw_supports_fid(fid) )
>      {
>          ret = FFA_RET_NOT_SUPPORTED;
> +        gdprintk(XENLOG_DEBUG, "ffa: run fid %#x not supported\n", fid);
>          goto out;
>      }
>
> @@ -322,6 +370,7 @@ void ffa_handle_run(struct cpu_user_regs *regs, uint32_t 
> fid)
>      if ( !FFA_ID_IS_SECURE(dst >> 16) )
>      {
>          ret = FFA_RET_NOT_SUPPORTED;
> +        gdprintk(XENLOG_DEBUG, "ffa: run to non-secure dst %#x\n", dst);
>          goto out;
>      }
>
> --
> 2.52.0
>