From 4c8859ec553bde224ac9841880caf40fb7c7e80e Mon Sep 17 00:00:00 2001
From: David Vrabel <david.vrabel@citrix.com>
Date: Tue, 15 Dec 2015 15:38:38 +0100
Subject: [PATCH 16/43] 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@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>
master commit: cea357ba4b3335ca5279ee9c00838f85575d5842
master date: 2015-12-02 15:19:53 +0100
---
 xen/arch/x86/mm/p2m-ept.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index 5e6ab3f..3f5138d 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -594,7 +594,6 @@ 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);
 
@@ -620,7 +619,7 @@ 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;
@@ -641,12 +640,7 @@ 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()) ||
@@ -689,8 +683,8 @@ 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
@@ -766,7 +760,7 @@ 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 non-nested p2m, may need to change VT-d page table.*/
-- 
2.7.2