[Xen-devel] [PATCH v6 5/7] VT-d: No need to set irq affinity for posted format IRTE

[Feng Wu <feng.wu@xxxxxxxxx>]

We don't set the affinity for posted format IRTE, since the
destination of these interrupts is vCPU and the vCPU affinity
is set during vCPU scheduling.

Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
---
v6:
- Make pi_can_suppress_irte_update() a check-only function
- Introduce another function pi_get_new_irte() to update the 'new_ire' if needed

v5:
- Only suppress affinity related IRTE updates for PI

v4:
- Keep the construction of new_ire and only modify the hardware
IRTE when it is not in posted mode.

 xen/drivers/passthrough/vtd/intremap.c | 61 ++++++++++++++++++++++++++++++++--
 1 file changed, 58 insertions(+), 3 deletions(-)

diff --git a/xen/drivers/passthrough/vtd/intremap.c 
b/xen/drivers/passthrough/vtd/intremap.c
index bfd468b..97e80a6 100644
--- a/xen/drivers/passthrough/vtd/intremap.c
+++ b/xen/drivers/passthrough/vtd/intremap.c
@@ -547,6 +547,54 @@ static int remap_entry_to_msi_msg(
     return 0;
 }
 
+static bool pi_can_suppress_irte_update(const struct iremap_entry *new,
+    const struct iremap_entry *old)
+{
+    ASSERT( old && new );
+
+    if ( !old->remap.p || !old->remap.im || !new->remap.p || new->remap.im )
+        return false;
+
+    /*
+     * We are updating posted IRTE to remapped one, check whether
+     * the common fields are going to be changed.
+     */
+    if ( ( new->remap.fpd != old->post.fpd ) ||
+         ( new->remap.sid != old->post.sid ) ||
+         ( new->remap.sq != old->post.sq ) ||
+         ( new->remap.svt != old->post.svt ) )
+        return false;
+
+    return true;
+}
+
+static void pi_get_new_irte(struct iremap_entry *new,
+    const struct iremap_entry *old)
+{
+    u16 fpd, sid, sq, svt;
+
+    ASSERT( old && new );
+
+    fpd = new->remap.fpd;
+    sid = new->remap.sid;
+    sq = new->remap.sq;
+    svt = new->remap.svt;
+
+    *new = *old;
+
+    if ( fpd != old->post.fpd )
+        new->post.fpd = fpd;
+
+    if ( sid != old->post.sid )
+        new->post.sid = sid;
+
+    if ( sq != old->post.sq )
+        new->post.sq = sq;
+
+    if ( svt != old->post.svt )
+        new->post.svt = svt;
+}
+
 static int msi_msg_to_remap_entry(
     struct iommu *iommu, struct pci_dev *pdev,
     struct msi_desc *msi_desc, struct msi_msg *msg)
@@ -637,9 +685,16 @@ static int msi_msg_to_remap_entry(
     remap_rte->address_hi = 0;
     remap_rte->data = index - i;
 
-    memcpy(iremap_entry, &new_ire, sizeof(struct iremap_entry));
-    iommu_flush_cache_entry(iremap_entry, sizeof(struct iremap_entry));
-    iommu_flush_iec_index(iommu, 0, index);
+    if ( !pi_can_suppress_irte_update(&new_ire, iremap_entry) )
+    {
+        if ( iremap_entry->remap.p && iremap_entry->remap.im &&
+             new_ire.remap.p && !new_ire.remap.im )
+            pi_get_new_irte(&new_ire, iremap_entry);
+
+        memcpy(iremap_entry, &new_ire, sizeof(struct iremap_entry));
+        iommu_flush_cache_entry(iremap_entry, sizeof(struct iremap_entry));
+        iommu_flush_iec_index(iommu, 0, index);
+    }
 
     unmap_vtd_domain_page(iremap_entries);
     spin_unlock_irqrestore(&ir_ctrl->iremap_lock, flags);
-- 
2.1.0


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