[PATCH v4 3/9] x86/passthrough: Extract pt_irq_dpci_setup() from pt_irq_create_bind()

[Julian Vetter <julian.vetter@xxxxxxxxxx>]

The setup preamble in pt_irq_create_bind(), lazily allocating
hvm_irq_dpci, looking up the struct pirq, and spinning until any pending
hvm_dirq_assist softirq has drained, is needed by pt_irq_bind_msi() as
well. Extract it into a static helper pt_irq_dpci_setup() that returns
with d->event_lock write-locked on success. Replace the open-coded goto
restart loop with a do { } while (true) loop and a continue, making the
retry structure explicit without a label. No functional change.

Signed-off-by: Julian Vetter <julian.vetter@xxxxxxxxxx>
---
Changes in v4:
- New patch
- Split out as a preparatory no-functional-change step to make the diff
  in patch 5 (pt_irq_bind_msi() interface change) easier to review
---
 xen/drivers/passthrough/x86/hvm.c | 54 +++++++++++++++++++++++--------
 1 file changed, 40 insertions(+), 14 deletions(-)

diff --git a/xen/drivers/passthrough/x86/hvm.c 
b/xen/drivers/passthrough/x86/hvm.c
index 691fa1b2c7..19463c3406 100644
--- a/xen/drivers/passthrough/x86/hvm.c
+++ b/xen/drivers/passthrough/x86/hvm.c
@@ -217,18 +217,22 @@ static struct vcpu *vector_hashing_dest(const struct 
domain *d,
     return dest;
 }
 
-int pt_irq_create_bind(
-    struct domain *d, const struct xen_domctl_bind_pt_irq *pt_irq_bind)
+/*
+ * Acquire d->event_lock (write), lazily allocate hvm_irq_dpci if needed, look
+ * up the struct pirq for @pirq, and drain any pending hvm_dirq_assist softirq
+ * on it before returning. Returns 0 with d->event_lock held on success,
+ * negative errno otherwise (lock not held).
+ */
+static int pt_irq_dpci_setup(struct domain *d, unsigned int pirq,
+                              struct hvm_irq_dpci **hvm_irq_dpci_out,
+                              struct hvm_pirq_dpci **pirq_dpci_out,
+                              struct pirq **info_out)
 {
     struct hvm_irq_dpci *hvm_irq_dpci;
     struct hvm_pirq_dpci *pirq_dpci;
     struct pirq *info;
-    int rc, pirq = pt_irq_bind->machine_irq;
 
-    if ( pirq < 0 || pirq >= d->nr_pirqs )
-        return -EINVAL;
-
- restart:
+    do
     {
         write_lock(&d->event_lock);
 
@@ -238,10 +242,11 @@ int pt_irq_create_bind(
             unsigned int i;
 
             /*
-             * NB: the hardware domain doesn't use a hvm_irq_dpci struct 
because
-             * it's only allowed to identity map GSIs, and so the data 
contained in
-             * that struct (used to map guest GSIs into machine GSIs and 
perform
-             * interrupt routing) is completely useless to it.
+             * NB: the hardware domain doesn't use a hvm_irq_dpci struct
+             * because it's only allowed to identity map GSIs, and so the
+             * data contained in that struct (used to map guest GSIs into
+             * machine GSIs and perform interrupt routing) is completely
+             * useless to it.
              */
             hvm_irq_dpci = xzalloc(struct hvm_irq_dpci);
             if ( hvm_irq_dpci == NULL )
@@ -269,15 +274,36 @@ int pt_irq_create_bind(
          * We MUST check for this condition as the softirq could be scheduled
          * and hasn't run yet. Note that this code replaced tasklet_kill which
          * would have spun forever and would do the same thing (wait to flush 
out
-         * outstanding hvm_dirq_assist calls.
+         * outstanding hvm_dirq_assist calls).
          */
         if ( pt_pirq_softirq_active(pirq_dpci) )
         {
             write_unlock(&d->event_lock);
             cpu_relax();
-            goto restart;
+            continue;
         }
-    }
+
+        *hvm_irq_dpci_out = hvm_irq_dpci;
+        *pirq_dpci_out = pirq_dpci;
+        *info_out = info;
+        return 0;
+    } while ( true );
+}
+
+int pt_irq_create_bind(
+    struct domain *d, const struct xen_domctl_bind_pt_irq *pt_irq_bind)
+{
+    struct hvm_irq_dpci *hvm_irq_dpci;
+    struct hvm_pirq_dpci *pirq_dpci;
+    struct pirq *info;
+    int rc, pirq = pt_irq_bind->machine_irq;
+
+    if ( pirq < 0 || pirq >= d->nr_pirqs )
+        return -EINVAL;
+
+    rc = pt_irq_dpci_setup(d, pirq, &hvm_irq_dpci, &pirq_dpci, &info);
+    if ( rc )
+        return rc;
 
     switch ( pt_irq_bind->irq_type )
     {
-- 
2.53.0



--
Julian Vetter | Vates Hypervisor & Kernel Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech