[RFC PATCH 3/7] common: Introduce needs_tlb_flush vcpu field

["Teddy Astie" <teddy.astie@xxxxxxxxxx>]

This field is meant to be used to schedule a TLB flush on the vCPU
before waking it up. This field can be set from another vCPU at any
time.

Schedule a TLB flush when the vCPU is migrated to another CPU.
This is needed as the vCPU-related TLB entries may be out of sync
with what happened on another core.

Currently, no architecture use this mechanism, but it is meant to
be used as a way to schedule a TLB flush on the vCPU.

Signed-off-by: Teddy Astie <teddy.astie@xxxxxxxxxx>
---
 xen/common/sched/core.c | 5 +++++
 xen/include/xen/sched.h | 2 ++
 2 files changed, 7 insertions(+)

diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
index a57d5dd929..f8e615b3af 100644
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -1188,7 +1188,12 @@ static void sched_unit_migrate_finish(struct sched_unit 
*unit)
 
     /* Wake on new CPU. */
     for_each_sched_unit_vcpu ( unit, v )
+    {
+        if ( old_cpu != new_cpu )
+            /* Migrating to another CPU needs TLB flush */
+            v->needs_tlb_flush = true;
         vcpu_wake(v);
+    }
 }
 
 static bool sched_check_affinity_broken(const struct sched_unit *unit)
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 4b8ae21b51..a26c571015 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -224,6 +224,8 @@ struct vcpu
     bool             defer_shutdown;
     /* VCPU is paused following shutdown request (d->is_shutting_down)? */
     bool             paused_for_shutdown;
+    /* VCPU needs its TLB flushed before waking. */
+    bool             needs_tlb_flush;
     /* VCPU need affinity restored */
     uint8_t          affinity_broken;
 #define VCPU_AFFINITY_OVERRIDE    0x01
-- 
2.52.0



--
Teddy Astie | Vates XCP-ng Developer

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