[Xen-changelog] [xen stable-4.5] x86/p2m-pt: tighten conditions of IOMMU mapping updates

[patchbot@xxxxxxx]

commit db0f474646878b0e91fd14f53eec6adcacc4b5ba
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Oct 8 11:38:44 2015 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Oct 8 11:38:44 2015 +0200

    x86/p2m-pt: tighten conditions of IOMMU mapping updates
    
    Whether the MFN changes does not depend on the new entry being valid
    (but solely on the old one), and the need to update or TLB-flush also
    depends on permission changes.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx>
    master commit: 660fd65d5578a95ec5eac522128bba23325179eb
    master date: 2015-10-02 13:40:36 +0200
---
 xen/arch/x86/mm/p2m-pt.c |   74 +++++++++++++++++++++++++++++-----------------
 1 files changed, 47 insertions(+), 27 deletions(-)

diff --git a/xen/arch/x86/mm/p2m-pt.c b/xen/arch/x86/mm/p2m-pt.c
index 1b71a7d..78512e6 100644
--- a/xen/arch/x86/mm/p2m-pt.c
+++ b/xen/arch/x86/mm/p2m-pt.c
@@ -493,7 +493,18 @@ p2m_pt_set_entry(struct p2m_domain *p2m, unsigned long 
gfn, mfn_t mfn,
     l3_pgentry_t l3e_content;
     int rc;
     unsigned int iommu_pte_flags = p2m_get_iommu_flags(p2mt);
-    unsigned long old_mfn = 0;
+    /*
+     * old_mfn and iommu_old_flags control possible flush/update needs on the
+     * IOMMU: We need to flush when MFN or flags (i.e. permissions) change.
+     * iommu_old_flags being initialized to zero covers the case of the entry
+     * getting replaced being a non-present (leaf or intermediate) one. For
+     * present leaf entries the real value will get calculated below, while
+     * for present intermediate entries ~0 (guaranteed != iommu_pte_flags)
+     * will be used (to cover all cases of what the leaf entries underneath
+     * the intermediate one might be).
+     */
+    unsigned int flags, iommu_old_flags = 0;
+    unsigned long old_mfn = INVALID_MFN;
 
     if ( tb_init_done )
     {
@@ -540,12 +551,20 @@ p2m_pt_set_entry(struct p2m_domain *p2m, unsigned long 
gfn, mfn_t mfn,
                                    L3_PAGETABLE_SHIFT - PAGE_SHIFT,
                                    L3_PAGETABLE_ENTRIES);
         ASSERT(p2m_entry);
-        if ( (l1e_get_flags(*p2m_entry) & _PAGE_PRESENT) &&
-             !(l1e_get_flags(*p2m_entry) & _PAGE_PSE) )
+        flags = l1e_get_flags(*p2m_entry);
+        if ( flags & _PAGE_PRESENT )
         {
-            /* We're replacing a non-SP page with a superpage.  Make sure to
-             * handle freeing the table properly. */
-            intermediate_entry = *p2m_entry;
+            if ( flags & _PAGE_PSE )
+            {
+                iommu_old_flags =
+                    p2m_get_iommu_flags(p2m_flags_to_type(flags));
+                old_mfn = l1e_get_pfn(*p2m_entry);
+            }
+            else
+            {
+                iommu_old_flags = ~0;
+                intermediate_entry = *p2m_entry;
+            }
         }
 
         ASSERT(!mfn_valid(mfn) || p2mt != p2m_mmio_direct);
@@ -556,10 +575,7 @@ p2m_pt_set_entry(struct p2m_domain *p2m, unsigned long 
gfn, mfn_t mfn,
         entry_content.l1 = l3e_content.l3;
 
         if ( entry_content.l1 != 0 )
-        {
             p2m_add_iommu_flags(&entry_content, 0, iommu_pte_flags);
-            old_mfn = l1e_get_pfn(*p2m_entry);
-        }
 
         p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 3);
         /* NB: paging_write_p2m_entry() handles tlb flushes properly */
@@ -584,7 +600,10 @@ p2m_pt_set_entry(struct p2m_domain *p2m, unsigned long 
gfn, mfn_t mfn,
         p2m_entry = p2m_find_entry(table, &gfn_remainder, gfn,
                                    0, L1_PAGETABLE_ENTRIES);
         ASSERT(p2m_entry);
-        
+        iommu_old_flags =
+            p2m_get_iommu_flags(p2m_flags_to_type(l1e_get_flags(*p2m_entry)));
+        old_mfn = l1e_get_pfn(*p2m_entry);
+
         if ( mfn_valid(mfn) || (p2mt == p2m_mmio_direct)
                             || p2m_is_paging(p2mt) )
             entry_content = p2m_l1e_from_pfn(mfn_x(mfn),
@@ -593,10 +612,8 @@ p2m_pt_set_entry(struct p2m_domain *p2m, unsigned long 
gfn, mfn_t mfn,
             entry_content = l1e_empty();
 
         if ( entry_content.l1 != 0 )
-        {
             p2m_add_iommu_flags(&entry_content, 0, iommu_pte_flags);
-            old_mfn = l1e_get_pfn(*p2m_entry);
-        }
+
         /* level 1 entry */
         p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 1);
         /* NB: paging_write_p2m_entry() handles tlb flushes properly */
@@ -607,14 +624,20 @@ p2m_pt_set_entry(struct p2m_domain *p2m, unsigned long 
gfn, mfn_t mfn,
                                    L2_PAGETABLE_SHIFT - PAGE_SHIFT,
                                    L2_PAGETABLE_ENTRIES);
         ASSERT(p2m_entry);
-        
-        /* FIXME: Deal with 4k replaced by 2meg pages */
-        if ( (l1e_get_flags(*p2m_entry) & _PAGE_PRESENT) &&
-             !(l1e_get_flags(*p2m_entry) & _PAGE_PSE) )
+        flags = l1e_get_flags(*p2m_entry);
+        if ( flags & _PAGE_PRESENT )
         {
-            /* We're replacing a non-SP page with a superpage.  Make sure to
-             * handle freeing the table properly. */
-            intermediate_entry = *p2m_entry;
+            if ( flags & _PAGE_PSE )
+            {
+                iommu_old_flags =
+                    p2m_get_iommu_flags(p2m_flags_to_type(flags));
+                old_mfn = l1e_get_pfn(*p2m_entry);
+            }
+            else
+            {
+                iommu_old_flags = ~0;
+                intermediate_entry = *p2m_entry;
+            }
         }
         
         ASSERT(!mfn_valid(mfn) || p2mt != p2m_mmio_direct);
@@ -628,10 +651,7 @@ p2m_pt_set_entry(struct p2m_domain *p2m, unsigned long 
gfn, mfn_t mfn,
         entry_content.l1 = l2e_content.l2;
 
         if ( entry_content.l1 != 0 )
-        {
             p2m_add_iommu_flags(&entry_content, 0, iommu_pte_flags);
-            old_mfn = l1e_get_pfn(*p2m_entry);
-        }
 
         p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 2);
         /* NB: paging_write_p2m_entry() handles tlb flushes properly */
@@ -642,17 +662,17 @@ p2m_pt_set_entry(struct p2m_domain *p2m, unsigned long 
gfn, mfn_t mfn,
          && (gfn + (1UL << page_order) - 1 > p2m->max_mapped_pfn) )
         p2m->max_mapped_pfn = gfn + (1UL << page_order) - 1;
 
-    if ( iommu_enabled && need_iommu(p2m->domain) )
+    if ( iommu_enabled && need_iommu(p2m->domain) &&
+         (iommu_old_flags != iommu_pte_flags || old_mfn != mfn_x(mfn)) )
     {
         if ( iommu_use_hap_pt(p2m->domain) )
         {
-            if ( old_mfn && (old_mfn != mfn_x(mfn)) )
+            if ( iommu_old_flags )
                 amd_iommu_flush_pages(p2m->domain, gfn, page_order);
         }
         else
         {
-            unsigned int flags = p2m_get_iommu_flags(p2mt);
-
+            flags = p2m_get_iommu_flags(p2mt);
             if ( flags != 0 )
                 for ( i = 0; i < (1UL << page_order); i++ )
                     iommu_map_page(p2m->domain, gfn+i, mfn_x(mfn)+i, flags);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.5

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