[PATCH v2.1 06/18] x86/pv: set/clear guest GDT mappings using {populate,destroy}_perdomain_mapping()

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

The pv_{set,destroy}_gdt() functions rely on the L1 table(s) that contain such
mappings being stashed in the domain structure, and thus such mappings being
modified by merely updating the L1 entries.

Switch both pv_{set,destroy}_gdt() to instead use
{populate,destory}_perdomain_mapping().

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Changes since v2:
 - Do not change ordering setup of arch_set_info_guest().
---
 xen/arch/x86/pv/descriptor-tables.c | 28 ++++++++++++----------------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/xen/arch/x86/pv/descriptor-tables.c 
b/xen/arch/x86/pv/descriptor-tables.c
index 02647a2c5047..5a79f022ce13 100644
--- a/xen/arch/x86/pv/descriptor-tables.c
+++ b/xen/arch/x86/pv/descriptor-tables.c
@@ -49,23 +49,20 @@ bool pv_destroy_ldt(struct vcpu *v)
 
 void pv_destroy_gdt(struct vcpu *v)
 {
-    l1_pgentry_t *pl1e = pv_gdt_ptes(v);
-    mfn_t zero_mfn = _mfn(virt_to_mfn(zero_page));
-    l1_pgentry_t zero_l1e = l1e_from_mfn(zero_mfn, __PAGE_HYPERVISOR_RO);
     unsigned int i;
 
     ASSERT(v == current || !vcpu_cpu_dirty(v));
 
-    v->arch.pv.gdt_ents = 0;
-    for ( i = 0; i < FIRST_RESERVED_GDT_PAGE; i++ )
-    {
-        mfn_t mfn = l1e_get_mfn(pl1e[i]);
+    if ( v->arch.cr3 )
+        destroy_perdomain_mapping(v, GDT_VIRT_START(v),
+                                  ARRAY_SIZE(v->arch.pv.gdt_frames));
 
-        if ( (l1e_get_flags(pl1e[i]) & _PAGE_PRESENT) &&
-             !mfn_eq(mfn, zero_mfn) )
-            put_page_and_type(mfn_to_page(mfn));
+    for ( i = 0; i < ARRAY_SIZE(v->arch.pv.gdt_frames); i++)
+    {
+        if ( !v->arch.pv.gdt_frames[i] )
+            break;
 
-        l1e_write(&pl1e[i], zero_l1e);
+        put_page_and_type(mfn_to_page(_mfn(v->arch.pv.gdt_frames[i])));
         v->arch.pv.gdt_frames[i] = 0;
     }
 }
@@ -74,8 +71,8 @@ int pv_set_gdt(struct vcpu *v, const unsigned long frames[],
                unsigned int entries)
 {
     struct domain *d = v->domain;
-    l1_pgentry_t *pl1e;
     unsigned int i, nr_frames = DIV_ROUND_UP(entries, 512);
+    mfn_t mfns[ARRAY_SIZE(v->arch.pv.gdt_frames)];
 
     ASSERT(v == current || !vcpu_cpu_dirty(v));
 
@@ -90,6 +87,8 @@ int pv_set_gdt(struct vcpu *v, const unsigned long frames[],
         if ( !mfn_valid(mfn) ||
              !get_page_and_type(mfn_to_page(mfn), d, PGT_seg_desc_page) )
             goto fail;
+
+        mfns[i] = mfn;
     }
 
     /* Tear down the old GDT. */
@@ -97,12 +96,9 @@ int pv_set_gdt(struct vcpu *v, const unsigned long frames[],
 
     /* Install the new GDT. */
     v->arch.pv.gdt_ents = entries;
-    pl1e = pv_gdt_ptes(v);
     for ( i = 0; i < nr_frames; i++ )
-    {
         v->arch.pv.gdt_frames[i] = frames[i];
-        l1e_write(&pl1e[i], l1e_from_pfn(frames[i], __PAGE_HYPERVISOR_RW));
-    }
+    populate_perdomain_mapping(v, GDT_VIRT_START(v), mfns, nr_frames);
 
     return 0;
 
-- 
2.46.0