Re: [XEN PATCH v8 12/22] xen/arm: ffa: support mapping guest RX/TX buffers

[Julien Grall <julien@xxxxxxx>]

Hi Jens,

On 13/04/2023 08:14, Jens Wiklander wrote:
> +static uint32_t handle_rxtx_map(uint32_t fid, register_t tx_addr,
> +                                register_t rx_addr, uint32_t page_count)
> +{
> +    uint32_t ret = FFA_RET_INVALID_PARAMETERS;
> +    struct domain *d = current->domain;
> +    struct ffa_ctx *ctx = d->arch.tee;
> +    struct page_info *tx_pg;
> +    struct page_info *rx_pg;
> +    p2m_type_t t;
> +    void *rx;
> +    void *tx;
> +
> +    if ( !smccc_is_conv_64(fid) )
> +    {
> +        /*
> +         * Calls using the 32-bit calling convention must ignore the upper
> +         * 32 bits in the argument registers.
> +         */
> +        tx_addr &= UINT32_MAX;
> +        rx_addr &= UINT32_MAX;
> +    }
> +
> +    if ( page_count > FFA_MAX_RXTX_PAGE_COUNT ) {
Coding style:

if ( ... )
{

> +        printk(XENLOG_ERR "ffa: RXTX_MAP: error: %u pages requested (limit 
> %u)\n",
> +               page_count, FFA_MAX_RXTX_PAGE_COUNT);
> +        return FFA_RET_NOT_SUPPORTED;
> +    }
> +
> +    /* Already mapped */
> +    if ( ctx->rx )
> +        return FFA_RET_DENIED;
> +
> +    tx_pg = get_page_from_gfn(d, gfn_x(gaddr_to_gfn(tx_addr)), &t, P2M_ALLOC);
I might be missing something. Here you only get the reference on one 
page. Per the value of FFA_MAX_RXTX_PAGE_COUNT, it looks like the buffer 
can be up to 32 pages.
Can you clarify?

> +    if ( !tx_pg )
> +        return FFA_RET_INVALID_PARAMETERS;
> +    /* Only normal RAM for now */
> +    if ( !p2m_is_ram(t) )
p2m_is_ram() would allow RAM page marked read-only in stage-2. Is it 
intended?
If not, then I think you want to use t != p2m_ram_rw.

> +        goto err_put_tx_pg;
> +
> +    rx_pg = get_page_from_gfn(d, gfn_x(gaddr_to_gfn(rx_addr)), &t, P2M_ALLOC);
> +    if ( !tx_pg )
> +        goto err_put_tx_pg;
> +    /* Only normal RAM for now */
> +    if ( !p2m_is_ram(t) )
Same here.

> +        goto err_put_rx_pg;
> +
> +    tx = __map_domain_page_global(tx_pg);
> +    if ( !tx )
> +        goto err_put_rx_pg;
> +
> +    rx = __map_domain_page_global(rx_pg);
> +    if ( !rx )
> +        goto err_unmap_tx;
> +
> +    ctx->rx = rx;
> +    ctx->tx = tx;
> +    ctx->rx_pg = rx_pg;
> +    ctx->tx_pg = tx_pg;
> +    ctx->page_count = page_count;
> +    ctx->tx_is_free = true;
> +    return FFA_RET_OK;
Cheers,

--
Julien Grall