Re: [RFC PATCH 4/4] xen/arm: ffa: Enable VM to VM without firmware

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Jens,

> On 1 Nov 2024, at 11:44, Jens Wiklander <jens.wiklander@xxxxxxxxxx> wrote:
> 
> Hi Bertrand,
> 
> On Wed, Oct 16, 2024 at 11:22 AM Bertrand Marquis
> <bertrand.marquis@xxxxxxx> wrote:
>> 
>> When VM to VM support is activated and there is no suitable FF-A support
>> in the firmware, enable FF-A support for VMs to allow using it for VM to
>> VM communications.
>> If there is Optee running in the secure world and using the non FF-A
>> communication system, having CONFIG_FFA_VM_TO_VM could be non functional
>> (if optee is probed first) or Optee could be non functional (if FF-A is
>> probed first) so it is not recommended to activate the configuration
>> option for such systems.
>> 
>> To make buffer full notification work between VMs when there is not
>> firmware, rework the notification handling and modify the global flag to
>> only be used as check for firmware notification support instead.
>> 
>> Modify part_info_get to return the list of VMs when there is no firmware
>> support.
>> 
>> Signed-off-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
>> ---
>> xen/arch/arm/tee/ffa.c          |  11 +++
>> xen/arch/arm/tee/ffa_notif.c    | 118 ++++++++++++++++----------------
>> xen/arch/arm/tee/ffa_partinfo.c |   2 +
>> 3 files changed, 73 insertions(+), 58 deletions(-)
> 
> I think it is desirable or at least a good goal to be able to have all
> TEE configurations enabled at compile time.
> 
> For optee_probe() to succeed, a DT node with compatible
> "linaro,optee-tz" must be present, and a trusted OS responding with
> the UUID used by OP-TEE. False positives can be ruled out unless the
> system is grossly misconfigured and shouldn't be used.
> 
> If we could make the probe order deterministic with OP-TEE before
> FF-A, we should be OK. If there is an odd system with OP-TEE SMC ABI
> in the secure world that wants to use FF-A VM to VM, removing the
> "linaro,optee-tz" compatible node from DT is enough to disable
> optee_probe() without recompiling Xen.

I do agree with the deterministic argument but I am not sure having
the order forced is the right solution.

Maybe we could use a command line argument so that one could
select explicitly the tee:
tee=ffa / tee=optee

If we could prevent to modify the device tree that will probably make
things easier.

What do you think ?

Cheers
Bertrand

> 
> Cheers,
> Jens
> 
>> 
>> diff --git a/xen/arch/arm/tee/ffa.c b/xen/arch/arm/tee/ffa.c
>> index 21d41b452dc9..6d427864f3da 100644
>> --- a/xen/arch/arm/tee/ffa.c
>> +++ b/xen/arch/arm/tee/ffa.c
>> @@ -324,8 +324,11 @@ static int ffa_domain_init(struct domain *d)
>>     struct ffa_ctx *ctx;
>>     int ret;
>> 
>> +#ifndef CONFIG_FFA_VM_TO_VM
>>     if ( !ffa_fw_version )
>>         return -ENODEV;
>> +#endif
>> +
>>     /*
>>      * We are using the domain_id + 1 as the FF-A ID for VMs as FF-A ID 0 is
>>      * reserved for the hypervisor and we only support secure endpoints using
>> @@ -549,7 +552,15 @@ err_no_fw:
>>     bitmap_zero(ffa_fw_abi_supported, FFA_ABI_BITMAP_SIZE);
>>     printk(XENLOG_WARNING "ARM FF-A No firmware support\n");
>> 
>> +#ifdef CONFIG_FFA_VM_TO_VM
>> +    INIT_LIST_HEAD(&ffa_teardown_head);
>> +    init_timer(&ffa_teardown_timer, ffa_teardown_timer_callback, NULL, 0);
>> +
>> +    printk(XENLOG_INFO "ARM FF-A only available between VMs\n");
>> +    return true;
>> +#else
>>     return false;
>> +#endif
>> }
>> 
>> static const struct tee_mediator_ops ffa_ops =
>> diff --git a/xen/arch/arm/tee/ffa_notif.c b/xen/arch/arm/tee/ffa_notif.c
>> index 052b3e364a70..f2c87d1320de 100644
>> --- a/xen/arch/arm/tee/ffa_notif.c
>> +++ b/xen/arch/arm/tee/ffa_notif.c
>> @@ -16,7 +16,7 @@
>> 
>> #include "ffa_private.h"
>> 
>> -static bool __ro_after_init notif_enabled;
>> +static bool __ro_after_init fw_notif_enabled;
>> static unsigned int __ro_after_init notif_sri_irq;
>> 
>> int ffa_handle_notification_bind(struct cpu_user_regs *regs)
>> @@ -27,21 +27,17 @@ int ffa_handle_notification_bind(struct cpu_user_regs 
>> *regs)
>>     uint32_t bitmap_lo = get_user_reg(regs, 3);
>>     uint32_t bitmap_hi = get_user_reg(regs, 4);
>> 
>> -    if ( !notif_enabled )
>> -        return FFA_RET_NOT_SUPPORTED;
>> -
>>     if ( (src_dst & 0xFFFFU) != ffa_get_vm_id(d) )
>>         return FFA_RET_INVALID_PARAMETERS;
>> 
>>     if ( flags )    /* Only global notifications are supported */
>>         return FFA_RET_DENIED;
>> 
>> -    /*
>> -     * We only support notifications from SP so no need to check the sender
>> -     * endpoint ID, the SPMC will take care of that for us.
>> -     */
>> -    return ffa_simple_call(FFA_NOTIFICATION_BIND, src_dst, flags, bitmap_hi,
>> -                           bitmap_lo);
>> +    if ( FFA_ID_IS_SECURE(src_dst>>16) && fw_notif_enabled )
>> +        return ffa_simple_call(FFA_NOTIFICATION_BIND, src_dst, flags,
>> +                               bitmap_hi, bitmap_lo);
>> +
>> +    return FFA_RET_NOT_SUPPORTED;
>> }
>> 
>> int ffa_handle_notification_unbind(struct cpu_user_regs *regs)
>> @@ -51,32 +47,36 @@ int ffa_handle_notification_unbind(struct cpu_user_regs 
>> *regs)
>>     uint32_t bitmap_lo = get_user_reg(regs, 3);
>>     uint32_t bitmap_hi = get_user_reg(regs, 4);
>> 
>> -    if ( !notif_enabled )
>> -        return FFA_RET_NOT_SUPPORTED;
>> -
>>     if ( (src_dst & 0xFFFFU) != ffa_get_vm_id(d) )
>>         return FFA_RET_INVALID_PARAMETERS;
>> 
>> -    /*
>> -     * We only support notifications from SP so no need to check the
>> -     * destination endpoint ID, the SPMC will take care of that for us.
>> -     */
>> -    return  ffa_simple_call(FFA_NOTIFICATION_UNBIND, src_dst, 0, bitmap_hi,
>> -                            bitmap_lo);
>> +    if ( FFA_ID_IS_SECURE(src_dst>>16) && fw_notif_enabled )
>> +        return  ffa_simple_call(FFA_NOTIFICATION_UNBIND, src_dst, 0, 
>> bitmap_hi,
>> +                                bitmap_lo);
>> +
>> +    return FFA_RET_NOT_SUPPORTED;
>> }
>> 
>> void ffa_handle_notification_info_get(struct cpu_user_regs *regs)
>> {
>>     struct domain *d = current->domain;
>>     struct ffa_ctx *ctx = d->arch.tee;
>> +    bool notif_pending = false;
>> 
>> -    if ( !notif_enabled )
>> +#ifndef CONFIG_FFA_VM_TO_VM
>> +    if ( !fw_notif_enabled )
>>     {
>>         ffa_set_regs_error(regs, FFA_RET_NOT_SUPPORTED);
>>         return;
>>     }
>> +#endif
>> 
>> -    if ( test_and_clear_bool(ctx->notif.secure_pending) )
>> +    notif_pending = ctx->notif.secure_pending;
>> +#ifdef CONFIG_FFA_VM_TO_VM
>> +    notif_pending |= ctx->notif.buff_full_pending;
>> +#endif
>> +
>> +    if ( notif_pending )
>>     {
>>         /* A pending global notification for the guest */
>>         ffa_set_regs(regs, FFA_SUCCESS_64, 0,
>> @@ -103,11 +103,13 @@ void ffa_handle_notification_get(struct cpu_user_regs 
>> *regs)
>>     uint32_t w6 = 0;
>>     uint32_t w7 = 0;
>> 
>> -    if ( !notif_enabled )
>> +#ifndef CONFIG_FFA_VM_TO_VM
>> +    if ( !fw_notif_enabled )
>>     {
>>         ffa_set_regs_error(regs, FFA_RET_NOT_SUPPORTED);
>>         return;
>>     }
>> +#endif
>> 
>>     if ( (recv & 0xFFFFU) != ffa_get_vm_id(d) )
>>     {
>> @@ -115,7 +117,8 @@ void ffa_handle_notification_get(struct cpu_user_regs 
>> *regs)
>>         return;
>>     }
>> 
>> -    if ( flags & ( FFA_NOTIF_FLAG_BITMAP_SP | FFA_NOTIF_FLAG_BITMAP_SPM ) )
>> +    if ( fw_notif_enabled && (flags & ( FFA_NOTIF_FLAG_BITMAP_SP
>> +                                        | FFA_NOTIF_FLAG_BITMAP_SPM )) )
>>     {
>>         struct arm_smccc_1_2_regs arg = {
>>             .a0 = FFA_NOTIFICATION_GET,
>> @@ -170,15 +173,14 @@ int ffa_handle_notification_set(struct cpu_user_regs 
>> *regs)
>>     uint32_t bitmap_lo = get_user_reg(regs, 3);
>>     uint32_t bitmap_hi = get_user_reg(regs, 4);
>> 
>> -    if ( !notif_enabled )
>> -        return FFA_RET_NOT_SUPPORTED;
>> -
>>     if ( (src_dst >> 16) != ffa_get_vm_id(d) )
>>         return FFA_RET_INVALID_PARAMETERS;
>> 
>> -    /* Let the SPMC check the destination of the notification */
>> -    return ffa_simple_call(FFA_NOTIFICATION_SET, src_dst, flags, bitmap_lo,
>> -                           bitmap_hi);
>> +    if ( FFA_ID_IS_SECURE(src_dst>>16) && fw_notif_enabled )
>> +        return ffa_simple_call(FFA_NOTIFICATION_SET, src_dst, flags, 
>> bitmap_lo,
>> +                               bitmap_hi);
>> +
>> +    return FFA_RET_NOT_SUPPORTED;
>> }
>> 
>> #ifdef CONFIG_FFA_VM_TO_VM
>> @@ -190,7 +192,7 @@ void ffa_raise_rx_buffer_full(struct domain *d)
>>         return;
>> 
>>     if ( !test_and_set_bool(ctx->notif.buff_full_pending) )
>> -        vgic_inject_irq(d, d->vcpu[0], notif_sri_irq, true);
>> +        vgic_inject_irq(d, d->vcpu[0], GUEST_FFA_NOTIF_PEND_INTR_ID, true);
>> }
>> #endif
>> 
>> @@ -363,7 +365,7 @@ void ffa_notif_init_interrupt(void)
>> {
>>     int ret;
>> 
>> -    if ( notif_enabled && notif_sri_irq < NR_GIC_SGI )
>> +    if ( fw_notif_enabled && notif_sri_irq < NR_GIC_SGI )
>>     {
>>         /*
>>          * An error here is unlikely since the primary CPU has already
>> @@ -394,47 +396,47 @@ void ffa_notif_init(void)
>>     int ret;
>> 
>>     /* Only enable fw notification if all ABIs we need are supported */
>> -    if ( !(ffa_fw_supports_fid(FFA_NOTIFICATION_BITMAP_CREATE) &&
>> -           ffa_fw_supports_fid(FFA_NOTIFICATION_BITMAP_DESTROY) &&
>> -           ffa_fw_supports_fid(FFA_NOTIFICATION_GET) &&
>> -           ffa_fw_supports_fid(FFA_NOTIFICATION_INFO_GET_64)) )
>> -        return;
>> -
>> -    arm_smccc_1_2_smc(&arg, &resp);
>> -    if ( resp.a0 != FFA_SUCCESS_32 )
>> -        return;
>> -
>> -    irq = resp.a2;
>> -    notif_sri_irq = irq;
>> -    if ( irq >= NR_GIC_SGI )
>> -        irq_set_type(irq, IRQ_TYPE_EDGE_RISING);
>> -    ret = request_irq(irq, 0, notif_irq_handler, "FF-A notif", NULL);
>> -    if ( ret )
>> +    if ( ffa_fw_supports_fid(FFA_NOTIFICATION_BITMAP_CREATE) &&
>> +         ffa_fw_supports_fid(FFA_NOTIFICATION_BITMAP_DESTROY) &&
>> +         ffa_fw_supports_fid(FFA_NOTIFICATION_GET) &&
>> +         ffa_fw_supports_fid(FFA_NOTIFICATION_INFO_GET_64) )
>>     {
>> -        printk(XENLOG_ERR "ffa: request_irq irq %u failed: error %d\n",
>> -               irq, ret);
>> -        return;
>> -    }
>> +        arm_smccc_1_2_smc(&arg, &resp);
>> +        if ( resp.a0 != FFA_SUCCESS_32 )
>> +            return;
>> 
>> -    notif_enabled = true;
>> +        irq = resp.a2;
>> +        notif_sri_irq = irq;
>> +        if ( irq >= NR_GIC_SGI )
>> +            irq_set_type(irq, IRQ_TYPE_EDGE_RISING);
>> +        ret = request_irq(irq, 0, notif_irq_handler, "FF-A notif", NULL);
>> +        if ( ret )
>> +        {
>> +            printk(XENLOG_ERR "ffa: request_irq irq %u failed: error %d\n",
>> +                   irq, ret);
>> +            return;
>> +        }
>> +        fw_notif_enabled = true;
>> +    }
>> }
>> 
>> int ffa_notif_domain_init(struct domain *d)
>> {
>>     int32_t res;
>> 
>> -    if ( !notif_enabled )
>> -        return 0;
>> +    if ( fw_notif_enabled )
>> +    {
>> 
>> -    res = ffa_notification_bitmap_create(ffa_get_vm_id(d), d->max_vcpus);
>> -    if ( res )
>> -        return -ENOMEM;
>> +        res = ffa_notification_bitmap_create(ffa_get_vm_id(d), 
>> d->max_vcpus);
>> +        if ( res )
>> +            return -ENOMEM;
>> +    }
>> 
>>     return 0;
>> }
>> 
>> void ffa_notif_domain_destroy(struct domain *d)
>> {
>> -    if ( notif_enabled )
>> +    if ( fw_notif_enabled )
>>         ffa_notification_bitmap_destroy(ffa_get_vm_id(d));
>> }
>> diff --git a/xen/arch/arm/tee/ffa_partinfo.c 
>> b/xen/arch/arm/tee/ffa_partinfo.c
>> index d699a267cc76..2e09440fe6c2 100644
>> --- a/xen/arch/arm/tee/ffa_partinfo.c
>> +++ b/xen/arch/arm/tee/ffa_partinfo.c
>> @@ -128,12 +128,14 @@ void ffa_handle_partition_info_get(struct 
>> cpu_user_regs *regs)
>>         goto out;
>>     }
>> 
>> +#ifndef CONFIG_FFA_VM_TO_VM
>>     if ( !ffa_fw_supports_fid(FFA_PARTITION_INFO_GET) )
>>     {
>>         /* Just give an empty partition list to the caller */
>>         ret = FFA_RET_OK;
>>         goto out;
>>     }
>> +#endif
>> 
>>     ret = ffa_rx_acquire(d);
>>     if ( ret != FFA_RET_OK )
>> --
>> 2.47.0