Re: [PATCH v2 3/5] xen/arm: ffa: Add buffer full notification support

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Jens,

> On 20 Mar 2025, at 15:51, Jens Wiklander <jens.wiklander@xxxxxxxxxx> wrote:
> 
> Hi Bertrand,
> 
> On Mon, Mar 10, 2025 at 3:51 PM Bertrand Marquis
> <bertrand.marquis@xxxxxxx> wrote:
>> 
>> Add support to raise a Rx buffer full notification to a VM.
>> This function will be used for indirect message support between VM and
>> is only activated if CONFIG_FFA_VM_TO_VM is selected.
>> 
>> Even if there are 32 framework notifications possible, right now only
>> one is defined so the implementation is simplified to only handle the
>> buffer full notification using a boolean. If other framework
>> notifications have to be supported one day, the design will have to be
>> modified to handle it properly.
>> 
>> Signed-off-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
>> ---
>> Changes in v2:
>> - Code style fix
>> ---
>> xen/arch/arm/tee/ffa_notif.c   | 26 +++++++++++++++++++++-----
>> xen/arch/arm/tee/ffa_private.h | 13 +++++++++++++
>> 2 files changed, 34 insertions(+), 5 deletions(-)
>> 
>> diff --git a/xen/arch/arm/tee/ffa_notif.c b/xen/arch/arm/tee/ffa_notif.c
>> index 00efaf8f7353..d19aa5c5bef6 100644
>> --- a/xen/arch/arm/tee/ffa_notif.c
>> +++ b/xen/arch/arm/tee/ffa_notif.c
>> @@ -93,6 +93,7 @@ void ffa_handle_notification_info_get(struct cpu_user_regs 
>> *regs)
>> void ffa_handle_notification_get(struct cpu_user_regs *regs)
>> {
>>     struct domain *d = current->domain;
>> +    struct ffa_ctx *ctx = d->arch.tee;
>>     uint32_t recv = get_user_reg(regs, 1);
>>     uint32_t flags = get_user_reg(regs, 2);
>>     uint32_t w2 = 0;
>> @@ -132,11 +133,7 @@ void ffa_handle_notification_get(struct cpu_user_regs 
>> *regs)
>>          */
>>         if ( ( flags  & FFA_NOTIF_FLAG_BITMAP_SP ) &&
>>              ( flags & FFA_NOTIF_FLAG_BITMAP_SPM ) )
>> -        {
>> -                struct ffa_ctx *ctx = d->arch.tee;
>> -
>> -                ACCESS_ONCE(ctx->notif.secure_pending) = false;
>> -        }
>> +            ACCESS_ONCE(ctx->notif.secure_pending) = false;
>> 
>>         arm_smccc_1_2_smc(&arg, &resp);
>>         e = ffa_get_ret_code(&resp);
>> @@ -156,6 +153,12 @@ void ffa_handle_notification_get(struct cpu_user_regs 
>> *regs)
>>             w6 = resp.a6;
>>     }
>> 
>> +#ifdef CONFIG_FFA_VM_TO_VM
>> +    if ( flags & FFA_NOTIF_FLAG_BITMAP_HYP &&
>> +          test_and_clear_bool(ctx->notif.buff_full_pending) )
>> +        w7 = FFA_NOTIF_RX_BUFFER_FULL;
>> +#endif
>> +
>>     ffa_set_regs(regs, FFA_SUCCESS_32, 0, w2, w3, w4, w5, w6, w7);
>> }
>> 
>> @@ -178,6 +181,19 @@ int ffa_handle_notification_set(struct cpu_user_regs 
>> *regs)
>>                            bitmap_hi);
>> }
>> 
>> +#ifdef CONFIG_FFA_VM_TO_VM
>> +void ffa_raise_rx_buffer_full(struct domain *d)
>> +{
>> +    struct ffa_ctx *ctx = d->arch.tee;
>> +
>> +    if ( !ctx )
>> +        return;
>> +
>> +    if ( !test_and_set_bool(ctx->notif.buff_full_pending) )
>> +        vgic_inject_irq(d, d->vcpu[0], notif_sri_irq, true);
>> +}
>> +#endif
>> +
>> /*
>>  * Extract a 16-bit ID (index n) from the successful return value from
>>  * FFA_NOTIFICATION_INFO_GET_64 or FFA_NOTIFICATION_INFO_GET_32. IDs are
>> diff --git a/xen/arch/arm/tee/ffa_private.h b/xen/arch/arm/tee/ffa_private.h
>> index bd6877d8c632..1f5067d5d0c9 100644
>> --- a/xen/arch/arm/tee/ffa_private.h
>> +++ b/xen/arch/arm/tee/ffa_private.h
>> @@ -210,6 +210,8 @@
>> #define FFA_NOTIF_INFO_GET_ID_COUNT_SHIFT   7
>> #define FFA_NOTIF_INFO_GET_ID_COUNT_MASK    0x1F
>> 
>> +#define FFA_NOTIF_RX_BUFFER_FULL        BIT(0, U)
>> +
>> /* Feature IDs used with FFA_FEATURES */
>> #define FFA_FEATURE_NOTIF_PEND_INTR     0x1U
>> #define FFA_FEATURE_SCHEDULE_RECV_INTR  0x2U
>> @@ -298,6 +300,13 @@ struct ffa_ctx_notif {
>>      * pending global notifications.
>>      */
>>     bool secure_pending;
>> +
>> +#ifdef CONFIG_FFA_VM_TO_VM
>> +    /*
>> +     * Pending Hypervisor framework notifications
>> +     */
>> +    bool buff_full_pending;
>> +#endif
> 
> It doesn't matter if there are one or two bools in this struct.
> However, the ifdef prevents using IS_ENABLED(CONFIG_FFA_VM_TO_VM)
> instead of an ifdef in the logic controlling access to this field.

Agree, I will make this field present all the time and switch to IS_ENABLED when
now possible.

Cheers
Bertrand

> 
> Cheers,
> Jens
> 
>> };
>> 
>> struct ffa_ctx {
>> @@ -369,6 +378,10 @@ void ffa_handle_notification_info_get(struct 
>> cpu_user_regs *regs);
>> void ffa_handle_notification_get(struct cpu_user_regs *regs);
>> int ffa_handle_notification_set(struct cpu_user_regs *regs);
>> 
>> +#ifdef CONFIG_FFA_VM_TO_VM
>> +void ffa_raise_rx_buffer_full(struct domain *d);
>> +#endif
>> +
>> void ffa_handle_msg_send_direct_req(struct cpu_user_regs *regs, uint32_t 
>> fid);
>> int32_t ffa_handle_msg_send2(struct cpu_user_regs *regs);
>> 
>> --
>> 2.47.1