[Xen-changelog] [xen stable-4.6] x86/ept: remove unnecessary sync after resolving misconfigured entries

[patchbot@xxxxxxx]

commit 6e59151b50b8981a37b015ad1b10e4876eb20926
Author:     David Vrabel <david.vrabel@xxxxxxxxxx>
AuthorDate: Tue Dec 15 15:25:00 2015 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Dec 15 15:25:00 2015 +0100

    x86/ept: remove unnecessary sync after resolving misconfigured entries
    
    When using EPT, type changes are done with the following steps:
    
    1. Set entry as invalid (misconfigured) by settings a reserved memory
    type.
    
    2. Flush all EPT and combined translations (ept_sync_domain()).
    
    3. Fixup misconfigured entries as required (on EPT_MISCONFIG vmexits or
    when explicitly setting an entry.
    
    Since resolve_misconfig() only updates entries that were misconfigured,
    there is no need to invalidate any translations since the hardware
    does not cache misconfigured translations (vol 3, section 28.3.2).
    
    Remove the unnecessary (and very expensive) ept_sync_domain() calls).
    
    Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>
    master commit: cea357ba4b3335ca5279ee9c00838f85575d5842
    master date: 2015-12-02 15:19:53 +0100
---
 xen/arch/x86/mm/p2m-ept.c |   14 ++++----------
 1 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index 9860c6c..8418aad 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -642,7 +642,6 @@ bool_t ept_handle_misconfig(uint64_t gpa)
     spurious = curr->arch.hvm_vmx.ept_spurious_misconfig;
     rc = resolve_misconfig(p2m, PFN_DOWN(gpa));
     curr->arch.hvm_vmx.ept_spurious_misconfig = 0;
-    ept_sync_domain(p2m);
 
     p2m_unlock(p2m);
 
@@ -669,7 +668,7 @@ ept_set_entry(struct p2m_domain *p2m, unsigned long gfn, 
mfn_t mfn,
     int need_modify_vtd_table = 1;
     int vtd_pte_present = 0;
     unsigned int iommu_flags = p2m_get_iommu_flags(p2mt);
-    enum { sync_off, sync_on, sync_check } needs_sync = sync_check;
+    bool_t needs_sync = 1;
     ept_entry_t old_entry = { .epte = 0 };
     ept_entry_t new_entry = { .epte = 0 };
     struct ept_data *ept = &p2m->ept;
@@ -690,12 +689,7 @@ ept_set_entry(struct p2m_domain *p2m, unsigned long gfn, 
mfn_t mfn,
     /* Carry out any eventually pending earlier changes first. */
     ret = resolve_misconfig(p2m, gfn);
     if ( ret < 0 )
-    {
-        ept_sync_domain(p2m);
         return ret;
-    }
-    if ( ret > 0 )
-        needs_sync = sync_on;
 
     ASSERT((target == 2 && hvm_hap_has_1gb()) ||
            (target == 1 && hvm_hap_has_2mb()) ||
@@ -738,8 +732,8 @@ ept_set_entry(struct p2m_domain *p2m, unsigned long gfn, 
mfn_t mfn,
         /* We reached the target level. */
 
         /* No need to flush if the old entry wasn't valid */
-        if ( needs_sync == sync_check && !is_epte_present(ept_entry) )
-            needs_sync = sync_off;
+        if ( !is_epte_present(ept_entry) )
+            needs_sync = 0;
 
         /* If we're replacing a non-leaf entry with a leaf entry (1GiB or 
2MiB),
          * the intermediate tables will be freed below after the ept flush
@@ -821,7 +815,7 @@ ept_set_entry(struct p2m_domain *p2m, unsigned long gfn, 
mfn_t mfn,
         p2m->max_mapped_pfn = gfn + (1UL << order) - 1;
 
 out:
-    if ( needs_sync != sync_off )
+    if ( needs_sync )
         ept_sync_domain(p2m);
 
     /* For host p2m, may need to change VT-d page table.*/
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

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