x86/pv: update guest LDT mappings using the linear entries

The pv_map_ldt_shadow_page() and pv_destroy_ldt() 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 require L1 entries.

Switch pv_map_ldt_shadow_page() to unconditionally use the linear recursive, as
that logic is always called while the vCPU is running on the current pCPU.

For pv_destroy_ldt() use the linear mappings if the vCPU is the one currently
running on the pCPU, otherwise use destroy_mappings().

Note this requires keeping an array with the pages currently mapped at the LDT
area, as that allows dropping the extra taken page reference when removing the
mappings.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

diff --git a/xen/arch/x86/include/asm/domain.h b/xen/arch/x86/include/asm/domain.h
index b79d6badd71c4d96279555df62fad75fe817a2b6..b659cffc7f813d97d9a3ba207eb169e97b8ac349 100644 (file)
--- a/xen/arch/x86/include/asm/domain.h
+++ b/xen/arch/x86/include/asm/domain.h
@@ -523,6 +523,8 @@ struct pv_vcpu
     struct trap_info *trap_ctxt;
 
     unsigned long gdt_frames[FIRST_RESERVED_GDT_PAGE];
+    /* Max LDT entries is 8192, so 8192 * 8 = 64KiB (16 pages). */
+    mfn_t ldt_frames[16];
     unsigned long ldt_base;
     unsigned int gdt_ents, ldt_ents;
 

diff --git a/xen/arch/x86/pv/descriptor-tables.c b/xen/arch/x86/pv/descriptor-tables.c
index 5a79f022ce132fc0928778320f3b1246ecb0be67..95b598a4c0cfa5e7043b664afa2e4fdbf29ab455 100644 (file)
--- a/xen/arch/x86/pv/descriptor-tables.c
+++ b/xen/arch/x86/pv/descriptor-tables.c
@@ -20,28 +20,29 @@
  */
 bool pv_destroy_ldt(struct vcpu *v)
 {
-    l1_pgentry_t *pl1e;
+    const unsigned int nr_frames = ARRAY_SIZE(v->arch.pv.ldt_frames);
     unsigned int i, mappings_dropped = 0;
-    struct page_info *page;
 
     ASSERT(!in_irq());
 
     ASSERT(v == current || !vcpu_cpu_dirty(v));
 
-    pl1e = pv_ldt_ptes(v);
+    destroy_perdomain_mapping(v, LDT_VIRT_START(v), nr_frames);
 
-    for ( i = 0; i < 16; i++ )
+    for ( i = 0; i < nr_frames; i++ )
     {
-        if ( !(l1e_get_flags(pl1e[i]) & _PAGE_PRESENT) )
-            continue;
+        mfn_t mfn = v->arch.pv.ldt_frames[i];
+        struct page_info *page;
 
-        page = l1e_get_page(pl1e[i]);
-        l1e_write(&pl1e[i], l1e_empty());
-        mappings_dropped++;
+        if ( mfn_eq(mfn, INVALID_MFN) )
+            continue;
 
+        v->arch.pv.ldt_frames[i] = INVALID_MFN;
+        page = mfn_to_page(mfn);
         ASSERT_PAGE_IS_TYPE(page, PGT_seg_desc_page);
         ASSERT_PAGE_IS_DOMAIN(page, v->domain);
         put_page_and_type(page);
+        mappings_dropped++;
     }
 
     return mappings_dropped;

diff --git a/xen/arch/x86/pv/domain.c b/xen/arch/x86/pv/domain.c
index 7e8bffaae9a0d148c74e88bb283bba9813e3ab34..32d7488cc186be21255fd2378d6f314ff1ce876b 100644 (file)
--- a/xen/arch/x86/pv/domain.c
+++ b/xen/arch/x86/pv/domain.c
@@ -303,6 +303,7 @@ void pv_vcpu_destroy(struct vcpu *v)
 int pv_vcpu_initialise(struct vcpu *v)
 {
     struct domain *d = v->domain;
+    unsigned int i;
     int rc;
 
     ASSERT(!is_idle_domain(d));
@@ -311,6 +312,9 @@ int pv_vcpu_initialise(struct vcpu *v)
     if ( rc )
         return rc;
 
+    for ( i = 0; i < ARRAY_SIZE(v->arch.pv.ldt_frames); i++ )
+        v->arch.pv.ldt_frames[i] = INVALID_MFN;
+
     BUILD_BUG_ON(X86_NR_VECTORS * sizeof(*v->arch.pv.trap_ctxt) >
                  PAGE_SIZE);
     v->arch.pv.trap_ctxt = xzalloc_array(struct trap_info, X86_NR_VECTORS);

diff --git a/xen/arch/x86/pv/mm.c b/xen/arch/x86/pv/mm.c
index 187f5f6a3e8c05b6d73d8756fc891c30d16b8750..4853e619f2a7b3523b50793e9b32d93544f5783f 100644 (file)
--- a/xen/arch/x86/pv/mm.c
+++ b/xen/arch/x86/pv/mm.c
@@ -86,7 +86,8 @@ bool pv_map_ldt_shadow_page(unsigned int offset)
         return false;
     }
 
-    pl1e = &pv_ldt_ptes(curr)[offset >> PAGE_SHIFT];
+    curr->arch.pv.ldt_frames[offset >> PAGE_SHIFT] = page_to_mfn(page);
+    pl1e = &__linear_l1_table[l1_linear_offset(LDT_VIRT_START(curr) + offset)];
     l1e_add_flags(gl1e, _PAGE_RW);
 
     l1e_write(pl1e, gl1e);