Re: [PATCH v3 2/2] iommu/arm-smmu-v3: Adopt arm_smmu_event in handlers

[Pranjal Shrivastava <praan@google.com>]

On Fri, Oct 11, 2024 at 10:45:52AM +0000, Pranjal Shrivastava wrote:
> On Fri, Oct 11, 2024 at 11:21:48AM +0100, Robin Murphy wrote:
> > On 2024-10-11 8:55 am, Pranjal Shrivastava wrote:
> > > On Thu, Oct 03, 2024 at 03:53:15PM -0700, Nicolin Chen wrote:
> > > > On Thu, Oct 03, 2024 at 09:34:35PM +0000, Pranjal Shrivastava wrote:
> > > > > > The master and master_name are not that necessary to be in the
> > > > > > arm_smmu_event. I would keep both of them as local variables in
> > > > > > arm_smmu_handle_evt and pass master_name in to dump().
> > > > > 
> > > > > Hmm, right or maybe ONLY have the master_name in arm_smmu_event?
> > > > 
> > > > Just move both out of arm_smmu_event. Keep the master_name as a
> > > > local variable like the "master". You'd just need to pass it in
> > > > to the dump(). They both are in that same handle_evt().
> > > > 
> > > 
> > > Ack.
> > > 
> > > > > > > Also, shall we rename it to `arm_smmu_read_evt_info` ?
> > > > > > 
> > > > > > I'd probably use arm_smmu_event_get_from_raw()? Trying to high-
> > > > > > light struct arm_smmu_event v.s. u64 evt[EVTQ_ENT_DWORDS]. Yet,
> > > > > > no strong feeling about that.
> > > > > > 
> > > > > 
> > > > > Ack. How about `read_arm_smmu_event` :)
> > > > > Unless, we wanna follow the arm_smmu_<func> convention?
> > > > 
> > > > I think it'd be nicer if we do.
> > > > 
> > > 
> > > Ack. `arm_smmu_get_evt_from_raw` it is!
> > 
> > FWIW that sounds needlessly overcomplicated to me - the "raw" event array
> > should be a member of arm_smmu_event itself, since it seems silly to have
> > them separate with one pointing to the other when they have the exact same
> > scope and lifetime anyway. There still shouldn't need to be more than a
> > single logical step to process an evtq record into a finished
> > arm_smmu_event, just that that processing is now going to go a bit further
> > than simply le64_to_cpu().
> 
> Hmm, are you suggesting something like queue_remove_raw(q, event->raw)?
> OR do you mean we should have our own queue_parse_evt(q, &event) that
> parses out the raw event into an `arm_smmu_event` record eliminating the
> need for the `arm_smmu_read_evt_info` altogether?
> 
> Because we'd still need to store the raw event anyway since we're still
> logging the raw event.
> 
> I think we can go with the former, i.e. queue_remove_raw(q, event->raw)
> and then use ``arm_smmu_read_evt_info` to populate other `event` fields

Based on your comment, I was thinking like the attached sample code.
LMK if you were referring to something like that?

> 
> > Thanks,
> > Robin.
> 

Thanks,
Pranjal
--------------------------------------------------------------------------
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 0636b81eef79..5845793c0a41 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -1929,6 +1929,35 @@ static void arm_smmu_get_event_from_raw(struct arm_smmu_device *smmu, u64 *evt,
 	event->smmu = smmu;
 }
 
+static int queue_remove_raw(struct arm_smmu_queue *q
+			    struct arm_smmu_event *event)
+{
+	int ret;
+
+	ret = queue_remove_raw(q,event->raw);
+	if (ret)
+		return ret;
+
+	/* Parse out the event fields */
+	event->id = FIELD_GET(EVTQ_0_ID, evt[0]);
+	event->sid = FIELD_GET(EVTQ_0_SID, evt[0]);
+	event->ssid_valid = evt[0] & EVTQ_0_SSV;
+	event->ssid = event->ssid_valid ? FIELD_GET(EVTQ_0_SSID, evt[0]) : IOMMU_NO_PASID;
+	event->class = FIELD_GET(EVTQ_1_CLASS, evt[1]);
+	event->iova = FIELD_GET(EVTQ_2_ADDR, evt[2]);
+	event->ipa = FIELD_GET(EVTQ_3_IPA, evt[3]);
+	event->privileged = FIELD_GET(EVTQ_1_PnU, evt[1]);
+	event->instruction = FIELD_GET(EVTQ_1_InD, evt[1]);
+	event->s2 = FIELD_GET(EVTQ_1_S2, evt[1]);
+	event->read = FIELD_GET(EVTQ_1_RnW, evt[1]);
+	event->stag = FIELD_GET(EVTQ_1_STAG, evt[1]);
+	event->stall = evt[1] & EVTQ_1_STALL;
+	event->raw = evt;
+	event->smmu = smmu;
+
+	return 0;
+}
+
 static irqreturn_t arm_smmu_evtq_thread(int irq, void *dev)
 {
 	int ret;
@@ -1941,9 +1970,8 @@ static irqreturn_t arm_smmu_evtq_thread(int irq, void *dev)
 	u64 evt[EVTQ_ENT_DWORDS];
 
 	do {
-		while (!queue_remove_raw(q, evt)) {
+		while (!queue_remove_evt(q, &event)) {
 
-			arm_smmu_get_event_from_raw(smmu, evt, &event);
 			ret = arm_smmu_handle_evt(&event);
 			if (!ret || !__ratelimit(&rs))
 				continue;