[Xen-devel] [PATCH v1 08/14] x86/np2m: add np2m_schedule()

[Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>]

np2m maintenance is required for a nested vcpu during scheduling:

    1. On schedule-out: clear pCPU's bit in p2m->dirty_cpumask
                        to prevent useless IPIs.

    2. On schedule-in: check if np2m is up to date and wasn't flushed.

Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
---
RFC --> v1:
- np2m_schedule() now accepts NP2M_SCHEDLE_IN/OUT

 xen/arch/x86/mm/p2m.c     | 43 +++++++++++++++++++++++++++++++++++++++++++
 xen/include/asm-x86/p2m.h |  5 +++++
 2 files changed, 48 insertions(+)

diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 053df0c9aa..e5d2fed361 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -1875,6 +1875,49 @@ p2m_get_p2m(struct vcpu *v)
     return p2m_get_nestedp2m(v);
 }
 
+void np2m_schedule(int dir)
+{
+    struct nestedvcpu *nv = &vcpu_nestedhvm(current);
+    struct p2m_domain *p2m;
+
+    ASSERT(dir == NP2M_SCHEDLE_IN || dir == NP2M_SCHEDLE_OUT);
+
+    if ( !nestedhvm_enabled(current->domain) ||
+         !nestedhvm_vcpu_in_guestmode(current) ||
+         !nestedhvm_paging_mode_hap(current) )
+        return;
+
+    p2m = nv->nv_p2m;
+    if ( p2m )
+    {
+        bool np2m_valid;
+
+        p2m_lock(p2m);
+        np2m_valid = p2m->np2m_base == nhvm_vcpu_p2m_base(current) &&
+                     nv->np2m_generation == p2m->np2m_generation;
+        if ( dir == NP2M_SCHEDLE_OUT && np2m_valid )
+        {
+            /*
+             * The np2m is up to date but this vCPU will no longer use it,
+             * which means there are no reasons to send a flush IPI.
+             */
+            cpumask_clear_cpu(current->processor, p2m->dirty_cpumask);
+        }
+        else if ( dir == NP2M_SCHEDLE_IN )
+        {
+            if ( !np2m_valid )
+            {
+                /* This vCPU's np2m was flushed while it was not runnable */
+                hvm_asid_flush_core();
+                vcpu_nestedhvm(current).nv_p2m = NULL;
+            }
+            else
+                cpumask_set_cpu(current->processor, p2m->dirty_cpumask);
+        }
+        p2m_unlock(p2m);
+    }
+}
+
 unsigned long paging_gva_to_gfn(struct vcpu *v,
                                 unsigned long va,
                                 uint32_t *pfec)
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index 1a7002cbcd..f873dc4fd9 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -370,6 +370,11 @@ struct p2m_domain *p2m_get_nestedp2m(struct vcpu *v);
  */
 struct p2m_domain *p2m_get_p2m(struct vcpu *v);
 
+#define NP2M_SCHEDLE_IN  0
+#define NP2M_SCHEDLE_OUT 1
+
+void np2m_schedule(int dir);
+
 static inline bool_t p2m_is_hostp2m(const struct p2m_domain *p2m)
 {
     return p2m->p2m_class == p2m_host;
-- 
2.11.0


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