Hi Christoffer,

On 03/05/2017 10:01, Christoffer Dall wrote:

On Wed, May 03, 2017 at 08:53:36AM +0200, Auger Eric wrote:

quoted

Hi Christoffer,

On 30/04/2017 21:35, Christoffer Dall wrote:

quoted

On Fri, Apr 14, 2017 at 12:15:28PM +0200, Eric Auger wrote:

quoted

Add a generic lookup_table() helper whose role consists in
scanning a contiguous table located in guest RAM and applying
a callback on each entry. Entries can be handled as linked lists
since the callback may return an offset to the next entry and
also tell that an entry is the last one.

Helper functions also are added to compute the device/event ID
offset to the next DTE/ITE.

compute_next_devid_offset, compute_next_eventid_offset and
lookup_table will become static in subsequent patches

Signed-off-by: Eric Auger <eric.auger@redhat.com>

---
v4 -> v5:
- use kvm_read_guest

v3 -> v4:
- remove static to avoid compilation warning
- correct size computation in looup_table()
- defines now encode the number of bits used for devid and eventid offsets
- use BIT() - 1 to encode the max offets
---
 virt/kvm/arm/vgic/vgic-its.c | 93 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 93 insertions(+)

diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index 56c5123..c22b35d 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c

@@ -195,6 +195,8 @@ static struct its_ite *find_ite(struct vgic_its *its, u32 device_id,
 
 #define VITS_TYPER_IDBITS 16
 #define VITS_TYPER_DEVBITS 16
+#define VITS_DTE_MAX_DEVID_OFFSET	(BIT(14) - 1)
+#define VITS_ITE_MAX_EVENTID_OFFSET	(BIT(16) - 1)
 
 /*
  * Finds and returns a collection in the ITS collection table.

@@ -1674,6 +1676,97 @@ int vgic_its_attr_regs_access(struct kvm_device *dev,
 	return ret;
 }
 
+u32 compute_next_devid_offset(struct list_head *h, struct its_device *dev)
+{
+	struct list_head *e = &dev->dev_list;
+	struct its_device *next;
+	u32 next_offset;
+
+	if (e->next == h)
+		return 0;
+	next = list_entry(e->next, struct its_device, dev_list);
+	next_offset = next->device_id - dev->device_id;
+
+	return min_t(u32, next_offset, VITS_DTE_MAX_DEVID_OFFSET);
+}
+
+u32 compute_next_eventid_offset(struct list_head *h, struct its_ite *ite)
+{
+	struct list_head *e = &ite->ite_list;
+	struct its_ite *next;
+	u32 next_offset;
+
+	if (e->next == h)
+		return 0;
+	next = list_entry(e->next, struct its_ite, ite_list);
+	next_offset = next->event_id - ite->event_id;
+
+	return min_t(u32, next_offset, VITS_ITE_MAX_EVENTID_OFFSET);
+}
+
+/**
+ * entry_fn_t - Callback called on a table entry restore path
+ * @its: its handle
+ * @id: id of the entry
+ * @entry: pointer to the entry
+ * @opaque: pointer to an opaque data
+ * @next_offset: minimal ID offset to the next entry. 0 if this
+ * entry is the last one, 1 if the entry is invalid, >= 1 if an

eh, also, did you mean -1 if the entry is invalid?

no in case the entry is invalid, we tell the caller that it must inspect
the next entry, hence the next_offset = +1.

jjjjj
hmm, but you say aftterwards that >= 1 if an entry's next_offset field
was truly decoded, so this is confusing.  Perhaps it would make more
sense to get rid of the parameter entirely and change the return value
to say:

  Return: < 0 on error, 0 if the entry was the last one, and > 0 to
          indicate the offset to the next entry that must be processed
	  when scanning a table.

  Note that we return 1 for an invalid entry, because scanning a table
  in this case simply requires us looking at the next entry, but we may
  return >= to 1 if we found a valid entry and decoded the next field in
  the entry.

What do you think?

Yes I'm going to experiment that change.

Thanks

Eric

Thanks,
-Christoffer

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