Re: [PATCH v2 11/12] xen/arm: ffa: Add MEM_SHARE page diagnostics

[Jens Wiklander <jens.wiklander@xxxxxxxxxx>]

Hi Bertrand,

On Wed, Feb 11, 2026 at 6:16 PM Bertrand Marquis
<bertrand.marquis@xxxxxxx> wrote:
>
> MEM_SHARE failures in get_shm_pages() are silent, which makes malformed
> ranges and page mapping failures hard to diagnose.
>
> Add debug logging for page validation failures:
> - descriptor validation failures (unaligned, range short/overflow)
> - per-page mapping failures (unmapped GFN, wrong p2m type)
> - address overflow detection in range walks
>
> Ratelimit temporary reclaim failures and log permanent reclaim failures
> as errors.
>
> No functional changes.
>
> Signed-off-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
> ---
> Changes since v1:
> - use one print per error case instead of the previous system using
>   variables to classify and a single print site.
> ---
>  xen/arch/arm/tee/ffa_shm.c | 39 +++++++++++++++++++++++++++++++++++---
>  1 file changed, 36 insertions(+), 3 deletions(-)

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

Cheers,
Jens

>
> diff --git a/xen/arch/arm/tee/ffa_shm.c b/xen/arch/arm/tee/ffa_shm.c
> index 070babce9627..3d61caaeba78 100644
> --- a/xen/arch/arm/tee/ffa_shm.c
> +++ b/xen/arch/arm/tee/ffa_shm.c
> @@ -161,32 +161,62 @@ static int32_t get_shm_pages(struct domain *d, struct 
> ffa_shm_mem *shm,
>          addr = ACCESS_ONCE(range[n].address);
>
>          if ( !IS_ALIGNED(addr, FFA_PAGE_SIZE) )
> +        {
> +            gdprintk(XENLOG_DEBUG,
> +                     "ffa: mem share pages invalid: unaligned range %u 
> address %#lx\n",
> +                     n, (unsigned long)addr);
>              return FFA_RET_INVALID_PARAMETERS;
> +        }
>
>          for ( m = 0; m < page_count; m++ )
>          {
>              if ( pg_idx >= shm->page_count )
> +            {
> +                gdprintk(XENLOG_DEBUG,
> +                         "ffa: mem share pages invalid: range overflow rg %u 
> pg %u\n",
> +                         n, m);
>                  return FFA_RET_INVALID_PARAMETERS;
> +            }
>
>              if ( !ffa_safe_addr_add(addr, m) )
> +            {
> +                gdprintk(XENLOG_DEBUG,
> +                         "ffa: mem share pages invalid: addr overflow rg %u 
> pg %u base %#lx\n",
> +                         n, m, (unsigned long)addr);
>                  return FFA_RET_INVALID_PARAMETERS;
> +            }
>
>              gaddr = addr + m * FFA_PAGE_SIZE;
>              gfn = gaddr_to_gfn(gaddr);
>              shm->pages[pg_idx] = get_page_from_gfn(d, gfn_x(gfn), &t,
>                                                    P2M_ALLOC);
>              if ( !shm->pages[pg_idx] )
> +            {
> +                gdprintk(XENLOG_DEBUG,
> +                         "ffa: mem share pages invalid: gfn unmapped rg %u 
> pg %u addr %#lx\n",
> +                         n, m, (unsigned long)gaddr);
>                  return FFA_RET_DENIED;
> +            }
>              /* Only normal RW RAM for now */
>              if ( t != p2m_ram_rw )
> +            {
> +                gdprintk(XENLOG_DEBUG,
> +                         "ffa: mem share pages invalid: p2m type %u rg %u pg 
> %u addr %#lx\n",
> +                         t, n, m, (unsigned long)gaddr);
>                  return FFA_RET_DENIED;
> +            }
>              pg_idx++;
>          }
>      }
>
>      /* The ranges must add up */
>      if ( pg_idx < shm->page_count )
> +    {
> +        gdprintk(XENLOG_DEBUG,
> +                 "ffa: mem share pages invalid: range short pg %u\n",
> +                 pg_idx);
>          return FFA_RET_INVALID_PARAMETERS;
> +    }
>
>      return FFA_RET_OK;
>  }
> @@ -741,8 +771,10 @@ bool ffa_shm_domain_destroy(struct domain *d)
>               * A temporary error that may get resolved a bit later, it's
>               * worth retrying.
>               */
> -            printk(XENLOG_G_INFO "%pd: ffa: Failed to reclaim handle %#lx : 
> %d\n",
> -                   d, shm->handle, res);
> +            if ( printk_ratelimit() )
> +                printk(XENLOG_G_WARNING
> +                       "%pd: ffa: Failed to reclaim handle %#lx : %d\n",
> +                       d, shm->handle, res);
>              break; /* We will retry later */
>          default:
>              /*
> @@ -754,7 +786,8 @@ bool ffa_shm_domain_destroy(struct domain *d)
>               * FFA_RET_NO_MEMORY might be a temporary error as it it could
>               * succeed if retried later, but treat it as permanent for now.
>               */
> -            printk(XENLOG_G_INFO "%pd: ffa: Permanent failure to reclaim 
> handle %#lx : %d\n",
> +            printk(XENLOG_G_ERR
> +                   "%pd: ffa: Permanent failure to reclaim handle %#lx : 
> %d\n",
>                     d, shm->handle, res);
>
>              /*
> --
> 2.52.0
>