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Re: [XEN PATCH v2 5/5] xen/arm: ffa: support notification



Hi Bertrand & Jens,

On 24/04/2024 07:53, Bertrand Marquis wrote:
Hi Jens,

On 23 Apr 2024, at 17:26, Jens Wiklander <jens.wiklander@xxxxxxxxxx> wrote:

Hi Julien,

On Mon, Apr 22, 2024 at 1:40 PM Julien Grall <julien@xxxxxxx> wrote:

Hi Jens,

This is not a full review of the code. I will let Bertrand doing it.

On 22/04/2024 08:37, Jens Wiklander wrote:
+void ffa_notif_init(void)
+{
+    const struct arm_smccc_1_2_regs arg = {
+        .a0 = FFA_FEATURES,
+        .a1 = FFA_FEATURE_SCHEDULE_RECV_INTR,
+    };
+    struct arm_smccc_1_2_regs resp;
+    unsigned int irq;
+    int ret;
+
+    arm_smccc_1_2_smc(&arg, &resp);
+    if ( resp.a0 != FFA_SUCCESS_32 )
+        return;
+
+    irq = resp.a2;
+    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 I am not mistaken, ffa_notif_init() is only called once on the boot
CPU. However, request_irq() needs to be called on every CPU so the
callback is registered every where and the interrupt enabled.

I know the name of the function is rather confusing. So can you confirm
this is what you expected?

Good catch, no this wasn't what I expected. I'll need to change this.


[...]

diff --git a/xen/arch/arm/tee/ffa_private.h b/xen/arch/arm/tee/ffa_private.h
index 98236cbf14a3..ef8ffd4526bd 100644
--- a/xen/arch/arm/tee/ffa_private.h
+++ b/xen/arch/arm/tee/ffa_private.h
@@ -25,6 +25,7 @@
  #define FFA_RET_DENIED                  -6
  #define FFA_RET_RETRY                   -7
  #define FFA_RET_ABORTED                 -8
+#define FFA_RET_NO_DATA                 -9

  /* FFA_VERSION helpers */
  #define FFA_VERSION_MAJOR_SHIFT         16U
@@ -97,6 +98,18 @@
   */
  #define FFA_MAX_SHM_COUNT               32

+/*
+ * TODO How to manage the available SGIs? SGI 8-15 seem to be entirely
+ * unused, but that may change.

Are the value below intended for the guests? If so, can they be moved in
public/arch-arm.h along with the others guest interrupts?

Yes, I'll move it.


+ *
+ * SGI is the preferred delivery mechanism. SGIs 8-15 are normally not used
+ * by a guest as they in a non-virtualized system typically are assigned to
+ * the secure world. Here we're free to use SGI 8-15 since they are virtual
+ * and have nothing to do with the secure world.

Do you have a pointer to the specification?

There's one at the top of arch/arm/tee/ffa.c,
https://developer.arm.com/documentation/den0077/e
Do you want the link close to the defines when I've moved them to
public/arch-arm.h?
Or is it perhaps better to give a link to "Arm Base System
Architecture v1.0C", https://developer.arm.com/documentation/den0094/
instead?

I would say we need the link to Arm Base System Architecture in arch-arm.

+1

Cheers,

--
Julien Grall



 


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