Changes to support large shadow pages *correctly*.

[palacios.git] / palacios / src / palacios / mmu / vmm_shdw_pg_tlb_64.h

diff --git a/palacios/src/palacios/mmu/vmm_shdw_pg_tlb_64.h b/palacios/src/palacios/mmu/vmm_shdw_pg_tlb_64.h
index db59d7d..aff8034 100644 (file)
--- a/palacios/src/palacios/mmu/vmm_shdw_pg_tlb_64.h
+++ b/palacios/src/palacios/mmu/vmm_shdw_pg_tlb_64.h
@@ -332,23 +332,32 @@ static int handle_pde_shadow_pagefault_64(struct guest_info * info, addr_t fault
        return 0;
     }
 
-    // Handle as a shadow large page if possible
-    if (guest_pde->large_page 
-       && (info->vm_info->mem_align >= PAGE_SIZE_2MB)) {
-       if (handle_2MB_shadow_pagefault_pde_64(info, fault_addr, error_code, shadow_pde_access,
-                                              (pde64_2MB_t *)shadow_pde, (pde64_2MB_t *)guest_pde) == -1) {
-           PrintError("Error handling large pagefault with large page\n");
-           return -1;
-       } else {
-           return 0;
-       }
-    } 
-
     pte64_t * shadow_pt = NULL;
     pte64_t * guest_pt = NULL;
 
     // get the next shadow page level, allocate if not present
     if (shadow_pde_access == PT_ACCESS_NOT_PRESENT) {
+        // Check if  we can use large pages and the guest memory is properly aligned
+        // to potentially use a large page
+        if (info->use_large_pages && guest_pde->large_page 
+           && (info->vm_info->mem_align >= PAGE_SIZE_2MB)) {
+            // Check underlying physical memory map to see if a large page is viable
+           addr_t guest_pa = BASE_TO_PAGE_ADDR_2MB(((pde64_2MB_t *)guest_pde)->page_base_addr);
+           uint32_t max_size = v3_get_max_page_size(info, guest_pa, PAGE_SIZE_2MB);
+           if (max_size >= PAGE_SIZE_2MB) {
+               if (handle_2MB_shadow_pagefault_pde_64(info, fault_addr, error_code, shadow_pde_access,
+                                                      (pde64_2MB_t *)shadow_pde, (pde64_2MB_t *)guest_pde) ==  0) {
+                   return 0;
+               } else {
+                   PrintError("Error handling large pagefault with large page\n");
+                   return -1;
+               }
+           } else {
+               PrintDebug("Underlying physical memory map doesn't allow use of a large page.\n");
+           }
+           // Fallthrough to handle the region with small pages
+       }
+
        struct shadow_page_data * shdw_page = create_new_shadow_pt(info);
        shadow_pt = (pte64_t *)V3_VAddr((void *)shdw_page->page_pa);