Re: [XEN PATCH v11 05/14] xen/arm: ffa: support guest FFA_PARTITION_INFO_GET

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Jens,

> On 31 Jul 2023, at 14:15, Jens Wiklander <jens.wiklander@xxxxxxxxxx> wrote:
> 
> Adds support in the mediator to handle FFA_PARTITION_INFO_GET requests
> from a guest. The requests are forwarded to the SPMC and the response is
> translated according to the FF-A version in use by the guest.
> 
> Using FFA_PARTITION_INFO_GET changes the owner of the RX buffer to the
> caller (the guest in this case), so once it is done with the buffer it
> must be released using FFA_RX_RELEASE before another call can be made.
> 
> Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>

Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Cheers
Bertrand

> ---
> v10->v11
> - Fixing a typo in a comment and adding another comment as requested
> ---
> xen/arch/arm/tee/ffa.c | 134 +++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 134 insertions(+)
> 
> diff --git a/xen/arch/arm/tee/ffa.c b/xen/arch/arm/tee/ffa.c
> index 6c76c9885774..6c889bf97002 100644
> --- a/xen/arch/arm/tee/ffa.c
> +++ b/xen/arch/arm/tee/ffa.c
> @@ -166,7 +166,18 @@
> #define FFA_MSG_SEND                    0x8400006EU
> #define FFA_MSG_POLL                    0x8400006AU
> 
> +/*
> + * Structs below ending with _1_0 are defined in FF-A-1.0-REL and
> + * structs ending with _1_1 are defined in FF-A-1.1-REL0.
> + */
> +
> /* Partition information descriptor */
> +struct ffa_partition_info_1_0 {
> +    uint16_t id;
> +    uint16_t execution_context;
> +    uint32_t partition_properties;
> +};
> +
> struct ffa_partition_info_1_1 {
>     uint16_t id;
>     uint16_t execution_context;
> @@ -189,6 +200,7 @@ struct ffa_ctx {
>      */
>     uint16_t create_signal_count;
>     bool rx_is_free;
> +    spinlock_t lock;
> };
> 
> /* Negotiated FF-A version to use with the SPMC */
> @@ -203,9 +215,15 @@ static uint16_t subscr_vm_destroyed_count __read_mostly;
> /*
>  * Our rx/tx buffers shared with the SPMC. FFA_RXTX_PAGE_COUNT is the
>  * number of pages used in each of these buffers.
> + *
> + * The RX buffer is protected from concurrent usage with ffa_rx_buffer_lock.
> + * Note that the SPMC is also tracking the ownership of our RX buffer so
> + * for calls which uses our RX buffer to deliver a result we must call
> + * ffa_rx_release() to let the SPMC know that we're done with the buffer.
>  */
> static void *ffa_rx __read_mostly;
> static void *ffa_tx __read_mostly;
> +static DEFINE_SPINLOCK(ffa_rx_buffer_lock);
> 
> static bool ffa_get_version(uint32_t *vers)
> {
> @@ -512,6 +530,103 @@ static uint32_t handle_rxtx_unmap(void)
>     return FFA_RET_OK;
> }
> 
> +static int32_t handle_partition_info_get(uint32_t w1, uint32_t w2, uint32_t 
> w3,
> +                                         uint32_t w4, uint32_t w5,
> +                                         uint32_t *count)
> +{
> +    int32_t ret = FFA_RET_DENIED;
> +    struct domain *d = current->domain;
> +    struct ffa_ctx *ctx = d->arch.tee;
> +
> +    /*
> +     * FF-A v1.0 has w5 MBZ while v1.1 allows
> +     * FFA_PARTITION_INFO_GET_COUNT_FLAG to be non-zero.
> +     *
> +     * FFA_PARTITION_INFO_GET_COUNT is only using registers and not the
> +     * rxtx buffer so do the partition_info_get directly.
> +     */
> +    if ( w5 == FFA_PARTITION_INFO_GET_COUNT_FLAG &&
> +         ctx->guest_vers == FFA_VERSION_1_1 )
> +        return ffa_partition_info_get(w1, w2, w3, w4, w5, count);
> +    if ( w5 )
> +        return FFA_RET_INVALID_PARAMETERS;
> +
> +    if ( !ffa_rx )
> +        return FFA_RET_DENIED;
> +
> +    spin_lock(&ctx->lock);
> +    if ( !ctx->page_count || !ctx->rx_is_free )
> +        goto out;
> +    spin_lock(&ffa_rx_buffer_lock);
> +    ret = ffa_partition_info_get(w1, w2, w3, w4, w5, count);
> +    if ( ret )
> +        goto out_rx_buf_unlock;
> +    /*
> +     * ffa_partition_info_get() succeeded so we now own the RX buffer we
> +     * share with the SPMC. We must give it back using ffa_rx_release()
> +     * once we've copied the content.
> +     */
> +
> +    if ( ctx->guest_vers == FFA_VERSION_1_0 )
> +    {
> +        size_t n;
> +        struct ffa_partition_info_1_1 *src = ffa_rx;
> +        struct ffa_partition_info_1_0 *dst = ctx->rx;
> +
> +        if ( ctx->page_count * FFA_PAGE_SIZE < *count * sizeof(*dst) )
> +        {
> +            ret = FFA_RET_NO_MEMORY;
> +            goto out_rx_release;
> +        }
> +
> +        for ( n = 0; n < *count; n++ )
> +        {
> +            dst[n].id = src[n].id;
> +            dst[n].execution_context = src[n].execution_context;
> +            dst[n].partition_properties = src[n].partition_properties;
> +        }
> +    }
> +    else
> +    {
> +        size_t sz = *count * sizeof(struct ffa_partition_info_1_1);
> +
> +        if ( ctx->page_count * FFA_PAGE_SIZE < sz )
> +        {
> +            ret = FFA_RET_NO_MEMORY;
> +            goto out_rx_release;
> +        }
> +
> +
> +        memcpy(ctx->rx, ffa_rx, sz);
> +    }
> +    ctx->rx_is_free = false;
> +out_rx_release:
> +    ffa_rx_release();
> +out_rx_buf_unlock:
> +    spin_unlock(&ffa_rx_buffer_lock);
> +out:
> +    spin_unlock(&ctx->lock);
> +
> +    return ret;
> +}
> +
> +static int32_t handle_rx_release(void)
> +{
> +    int32_t ret = FFA_RET_DENIED;
> +    struct domain *d = current->domain;
> +    struct ffa_ctx *ctx = d->arch.tee;
> +
> +    spin_lock(&ctx->lock);
> +    if ( !ctx->page_count || ctx->rx_is_free )
> +        goto out;
> +    ret = FFA_RET_OK;
> +    ctx->rx_is_free = true;
> +out:
> +    spin_unlock(&ctx->lock);
> +
> +    return ret;
> +}
> +
> static void handle_msg_send_direct_req(struct cpu_user_regs *regs, uint32_t 
> fid)
> {
>     struct arm_smccc_1_2_regs arg = { .a0 = fid, };
> @@ -568,6 +683,7 @@ static bool ffa_handle_call(struct cpu_user_regs *regs)
>     uint32_t fid = get_user_reg(regs, 0);
>     struct domain *d = current->domain;
>     struct ffa_ctx *ctx = d->arch.tee;
> +    uint32_t count;
>     int e;
> 
>     if ( !ctx )
> @@ -597,6 +713,24 @@ static bool ffa_handle_call(struct cpu_user_regs *regs)
>         else
>             set_regs_success(regs, 0, 0);
>         return true;
> +    case FFA_PARTITION_INFO_GET:
> +        e = handle_partition_info_get(get_user_reg(regs, 1),
> +                                      get_user_reg(regs, 2),
> +                                      get_user_reg(regs, 3),
> +                                      get_user_reg(regs, 4),
> +                                      get_user_reg(regs, 5), &count);
> +        if ( e )
> +            set_regs_error(regs, e);
> +        else
> +            set_regs_success(regs, count, 0);
> +        return true;
> +    case FFA_RX_RELEASE:
> +        e = handle_rx_release();
> +        if ( e )
> +            set_regs_error(regs, e);
> +        else
> +            set_regs_success(regs, 0, 0);
> +        return true;
>     case FFA_MSG_SEND_DIRECT_REQ_32:
>     case FFA_MSG_SEND_DIRECT_REQ_64:
>         handle_msg_send_direct_req(regs, fid);
> -- 
> 2.34.1
>