[Xen-changelog] [xen master] x86/np2m: implement sharing of np2m between vCPUs

[patchbot@xxxxxxx]

commit 6df4b481b0c52ef2d432c1b3d3657369be4c1ea3
Author:     Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
AuthorDate: Tue Oct 3 16:21:02 2017 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Fri Oct 6 13:36:43 2017 +0100

    x86/np2m: implement sharing of np2m between vCPUs
    
    At the moment, nested p2ms are not shared between vcpus even if they
    share the same base pointer.
    
    Modify p2m_get_nestedp2m() to allow sharing a np2m between multiple
    vcpus with the same np2m_base (L1 np2m_base value in VMCx12).
    
    If the current np2m doesn't match the current base pointer, first look
    for another nested p2m in the same domain with the same base pointer,
    before reclaiming one from the LRU.
    
    Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
    Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Jun Nakajima <jun.nakajima@xxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vvmx.c |  1 +
 xen/arch/x86/mm/p2m.c       | 26 ++++++++++++++++++++++----
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c
index 198ca72..dde02c0 100644
--- a/xen/arch/x86/hvm/vmx/vvmx.c
+++ b/xen/arch/x86/hvm/vmx/vvmx.c
@@ -1201,6 +1201,7 @@ static void virtual_vmentry(struct cpu_user_regs *regs)
 
     /* Setup virtual ETP for L2 guest*/
     if ( nestedhvm_paging_mode_hap(v) )
+        /* This will setup the initial np2m for the nested vCPU */
         __vmwrite(EPT_POINTER, get_shadow_eptp(v));
     else
         __vmwrite(EPT_POINTER, get_host_eptp(v));
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 201b95d..0d47a13 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -1846,6 +1846,7 @@ p2m_get_nestedp2m_locked(struct vcpu *v)
     struct domain *d = v->domain;
     struct p2m_domain *p2m;
     uint64_t np2m_base = nhvm_vcpu_p2m_base(v);
+    unsigned int i;
 
     /* Mask out low bits; this avoids collisions with P2M_BASE_EADDR */
     np2m_base &= ~(0xfffull);
@@ -1859,19 +1860,19 @@ p2m_get_nestedp2m_locked(struct vcpu *v)
     if ( p2m ) 
     {
         p2m_lock(p2m);
-        if ( p2m->np2m_base == np2m_base || p2m->np2m_base == P2M_BASE_EADDR )
+        if ( p2m->np2m_base == np2m_base )
         {
             /* Check if np2m was flushed just before the lock */
-            if ( p2m->np2m_base == P2M_BASE_EADDR ||
-                 nv->np2m_generation != p2m->np2m_generation )
+            if ( nv->np2m_generation != p2m->np2m_generation )
                 nvcpu_flush(v);
+            /* np2m is up-to-date */
             p2m->np2m_base = np2m_base;
             assign_np2m(v, p2m);
             nestedp2m_unlock(d);
 
             return p2m;
         }
-        else
+        else if ( p2m->np2m_base != P2M_BASE_EADDR )
         {
             /* vCPU is switching from some other valid np2m */
             cpumask_clear_cpu(v->processor, p2m->dirty_cpumask);
@@ -1879,6 +1880,23 @@ p2m_get_nestedp2m_locked(struct vcpu *v)
         p2m_unlock(p2m);
     }
 
+    /* Share a np2m if possible */
+    for ( i = 0; i < MAX_NESTEDP2M; i++ )
+    {
+        p2m = d->arch.nested_p2m[i];
+        p2m_lock(p2m);
+        if ( p2m->np2m_base == np2m_base )
+        {
+            nvcpu_flush(v);
+            p2m->np2m_base = np2m_base;
+            assign_np2m(v, p2m);
+            nestedp2m_unlock(d);
+
+            return p2m;
+        }
+        p2m_unlock(p2m);
+    }
+
     /* All p2m's are or were in use. Take the least recent used one,
      * flush it and reuse. */
     p2m = p2m_getlru_nestedp2m(d, NULL);
--
generated by git-patchbot for /home/xen/git/xen.git#master

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