[Xen-changelog] [xen master] x86/ept: invalidate guest physical mappings on VMENTER

[patchbot@xxxxxxx]

commit 8eb2235599925b508bcbeb3402aba21fa2c266fd
Author:     David Vrabel <david.vrabel@xxxxxxxxxx>
AuthorDate: Mon Dec 21 13:36:41 2015 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Dec 21 13:36:41 2015 +0100

    x86/ept: invalidate guest physical mappings on VMENTER
    
    If a guest allocates a page and the tlbflush_timestamp on the page
    indicates that a TLB flush of the previous owner is required, only the
    linear and combined mappings are invalidated.  The guest-physical
    mappings are not invalidated.
    
    This is currently safe because the EPT code ensures that the
    guest-physical and combined mappings are invalidated /before/ the page
    is freed.  However, this prevents us from deferring the EPT invalidate
    until after the page is freed (e.g., to defer the invalidate until the
    p2m locks are released).
    
    The TLB flush that may be done after allocating page already causes
    the original guest to VMEXIT, thus on VMENTER we can do an INVEPT if
    one is pending.
    
    This means __ept_sync_domain() need not do anything and the thus the
    on_selected_cpu() call does not need to wait for as long.
    
    ept_sync_domain() now marks all PCPUs as needing to be invalidated,
    including PCPUs that the domain has not run on.  We still only IPI
    those PCPUs that are active so this does not result in any more INVEPT
    calls.
    
    We do not attempt to track when PCPUs may have cached translations
    because the only safe way to clear this per-CPU state is if
    immediately after an invalidate the PCPU is not active (i.e., the PCPU
    is not in d->domain_dirty_cpumask).  Since we only invalidate on
    VMENTER or by IPIing active PCPUs this can never happen.
    
    Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
    Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx>
    Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmx.c         |   24 ++++++++++++------------
 xen/arch/x86/mm/p2m-ept.c          |   31 ++++++++++++++++++-------------
 xen/include/asm-x86/hvm/vmx/vmcs.h |    4 ++--
 3 files changed, 32 insertions(+), 27 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index e056515..bda94a9 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -744,24 +744,12 @@ static void vmx_ctxt_switch_from(struct vcpu *v)
 
 static void vmx_ctxt_switch_to(struct vcpu *v)
 {
-    struct domain *d = v->domain;
     unsigned long old_cr4 = read_cr4(), new_cr4 = mmu_cr4_features;
-    struct ept_data *ept_data = &p2m_get_hostp2m(d)->ept;
 
     /* HOST_CR4 in VMCS is always mmu_cr4_features. Sync CR4 now. */
     if ( old_cr4 != new_cr4 )
         write_cr4(new_cr4);
 
-    if ( paging_mode_hap(d) )
-    {
-        unsigned int cpu = smp_processor_id();
-        /* Test-and-test-and-set this CPU in the EPT-is-synced mask. */
-        if ( !cpumask_test_cpu(cpu, ept_get_synced_mask(ept_data)) &&
-             !cpumask_test_and_set_cpu(cpu,
-                                       ept_get_synced_mask(ept_data)) )
-            __invept(INVEPT_SINGLE_CONTEXT, ept_get_eptp(ept_data), 0);
-    }
-
     vmx_restore_guest_msrs(v);
     vmx_restore_dr(v);
 }
@@ -3590,6 +3578,18 @@ void vmx_vmenter_helper(const struct cpu_user_regs *regs)
     if ( unlikely(need_flush) )
         vpid_sync_all();
 
+    if ( paging_mode_hap(curr->domain) )
+    {
+        struct ept_data *ept = &p2m_get_hostp2m(curr->domain)->ept;
+        unsigned int cpu = smp_processor_id();
+
+        if ( cpumask_test_cpu(cpu, ept->invalidate) )
+        {
+            cpumask_clear_cpu(cpu, ept->invalidate);
+            __invept(INVEPT_SINGLE_CONTEXT, ept_get_eptp(ept), 0);
+        }
+    }
+
  out:
     HVMTRACE_ND(VMENTRY, 0, 1/*cycles*/, 0, 0, 0, 0, 0, 0, 0);
 
diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index eef0372..c094320 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -1089,9 +1089,10 @@ static void ept_memory_type_changed(struct p2m_domain 
*p2m)
 
 static void __ept_sync_domain(void *info)
 {
-    struct ept_data *ept = &((struct p2m_domain *)info)->ept;
-
-    __invept(INVEPT_SINGLE_CONTEXT, ept_get_eptp(ept), 0);
+    /*
+     * The invalidation will be done before VMENTER (see
+     * vmx_vmenter_helper()).
+     */
 }
 
 void ept_sync_domain(struct p2m_domain *p2m)
@@ -1108,15 +1109,15 @@ void ept_sync_domain(struct p2m_domain *p2m)
         p2m_flush_nestedp2m(d);
 
     /*
-     * Flush active cpus synchronously. Flush others the next time this domain
-     * is scheduled onto them. We accept the race of other CPUs adding to
-     * the ept_synced mask before on_selected_cpus() reads it, resulting in
-     * unnecessary extra flushes, to avoid allocating a cpumask_t on the stack.
+     * Need to invalidate on all PCPUs because either:
+     *
+     * a) A VCPU has run and some translations may be cached.
+     * b) A VCPU has not run and and the initial invalidation in case
+     *    of an EP4TA reuse is still needed.
      */
-    cpumask_and(ept_get_synced_mask(ept),
-                d->domain_dirty_cpumask, &cpu_online_map);
+    cpumask_setall(ept->invalidate);
 
-    on_selected_cpus(ept_get_synced_mask(ept),
+    on_selected_cpus(d->domain_dirty_cpumask,
                      __ept_sync_domain, p2m, 1);
 }
 
@@ -1182,10 +1183,14 @@ int ept_p2m_init(struct p2m_domain *p2m)
         p2m->flush_hardware_cached_dirty = ept_flush_pml_buffers;
     }
 
-    if ( !zalloc_cpumask_var(&ept->synced_mask) )
+    if ( !zalloc_cpumask_var(&ept->invalidate) )
         return -ENOMEM;
 
-    on_each_cpu(__ept_sync_domain, p2m, 1);
+    /*
+     * Assume an initial invalidation is required, in case an EP4TA is
+     * reused.
+     */
+    cpumask_setall(ept->invalidate);
 
     return 0;
 }
@@ -1193,7 +1198,7 @@ int ept_p2m_init(struct p2m_domain *p2m)
 void ept_p2m_uninit(struct p2m_domain *p2m)
 {
     struct ept_data *ept = &p2m->ept;
-    free_cpumask_var(ept->synced_mask);
+    free_cpumask_var(ept->invalidate);
 }
 
 static void ept_dump_p2m_table(unsigned char key)
diff --git a/xen/include/asm-x86/hvm/vmx/vmcs.h 
b/xen/include/asm-x86/hvm/vmx/vmcs.h
index a8d4d5b..d1496b8 100644
--- a/xen/include/asm-x86/hvm/vmx/vmcs.h
+++ b/xen/include/asm-x86/hvm/vmx/vmcs.h
@@ -67,7 +67,8 @@ struct ept_data {
         };
         u64 eptp;
     };
-    cpumask_var_t synced_mask;
+    /* Set of PCPUs needing an INVEPT before a VMENTER. */
+    cpumask_var_t invalidate;
 };
 
 #define _VMX_DOMAIN_PML_ENABLED    0
@@ -97,7 +98,6 @@ struct pi_desc {
 #define ept_get_wl(ept)   ((ept)->ept_wl)
 #define ept_get_asr(ept)  ((ept)->asr)
 #define ept_get_eptp(ept) ((ept)->eptp)
-#define ept_get_synced_mask(ept) ((ept)->synced_mask)
 
 #define NR_PML_ENTRIES   512
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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