[Xen-devel] [PATCH 2 of 2] Added a hook for clearing ptes when a vma is freed by the kernel. Adapted from gntdev

[Geoffrey Lefebvre <geoffrey@xxxxxxxxx>]

# HG changeset patch
# User Geoffrey Lefebvre <geoffrey@xxxxxxxxx>
# Date 1179788664 25200
# Node ID 236647990e986bca16f150c2fca87c0ed1ebd729
# Parent  f5218394705702c1aaa02520be2ba5a9f2648f37
Added a hook for clearing ptes when a vma is freed by the kernel. Adapted from 
gntdev.

diff -r f52183947057 -r 236647990e98 
linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c
--- a/linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c  Mon May 21 16:01:52 
2007 -0700
+++ b/linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c  Mon May 21 16:04:24 
2007 -0700
@@ -269,6 +269,16 @@ static inline int GET_NEXT_REQ(unsigned 
        return INVALID_REQ;
 }
 
+static inline int OFFSET_TO_USR_IDX(int offset)
+{
+       return offset / BLKIF_MAX_SEGMENTS_PER_REQUEST;
+}
+
+static inline int OFFSET_TO_SEG(int offset)
+{
+       return offset % BLKIF_MAX_SEGMENTS_PER_REQUEST;
+}
+
 
 #define BLKTAP_INVALID_HANDLE(_g) \
     (((_g->kernel) == INVALID_GRANT_HANDLE) &&  \
@@ -295,8 +305,94 @@ static struct page *blktap_nopage(struct
        return NOPAGE_SIGBUS;
 }
 
+static pte_t blktap_clear_pte(struct vm_area_struct *vma,
+                             unsigned long uvaddr,
+                             pte_t *ptep, int is_fullmm)
+{
+       pte_t copy = *ptep;
+       tap_blkif_t *info;
+       int offset, seg, usr_idx, pending_idx, mmap_idx;
+       unsigned long uvstart = vma->vm_start + (RING_PAGES << PAGE_SHIFT);
+       unsigned long kvaddr;
+       struct page **map;
+       struct page *pg;
+       struct grant_handle_pair *khandle;
+       struct gnttab_unmap_grant_ref unmap[2];
+       int count = 0;
+       static int print_warning = 1;
+
+       /*print a warning message once, if the hook gets called*/
+       if (print_warning) {
+               WPRINTK("Clear pte hook called!\n");
+               print_warning = 0;
+       }
+
+       /* If the address is before the start of the grant mapped region
+        * or if vm_file is NULL (meaning mmap failed and we have nothing to do)
+        */
+       if (uvaddr < uvstart || vma->vm_file == NULL)
+               return copy;
+
+       info = vma->vm_file->private_data;
+       map = vma->vm_private_data;
+
+       /* TODO Should these be changed to if statements? */
+       BUG_ON(!info);
+       BUG_ON(!info->idx_map);
+       BUG_ON(!map);
+
+       offset = (int) ((uvaddr - uvstart) >> PAGE_SHIFT);
+       usr_idx = OFFSET_TO_USR_IDX(offset);
+       seg = OFFSET_TO_SEG(offset);
+
+       pending_idx = MASK_PEND_IDX(ID_TO_IDX(info->idx_map[usr_idx]));
+       mmap_idx = ID_TO_MIDX(info->idx_map[usr_idx]);
+
+       kvaddr = idx_to_kaddr(mmap_idx, pending_idx, seg);
+       pg = pfn_to_page(__pa(kvaddr) >> PAGE_SHIFT);
+       ClearPageReserved(pg);
+       map[offset] = NULL;
+
+       khandle = &pending_handle(mmap_idx, pending_idx, seg);
+
+       if (khandle->kernel != INVALID_GRANT_HANDLE) {
+       
+               gnttab_set_unmap_op(&unmap[count], kvaddr, 
+                                   GNTMAP_host_map, khandle->kernel);
+               count++;
+
+               set_phys_to_machine(__pa(kvaddr) >> PAGE_SHIFT, 
+                                   INVALID_P2M_ENTRY);
+       }
+
+       if (khandle->user != INVALID_GRANT_HANDLE) {
+
+               BUG_ON(xen_feature(XENFEAT_auto_translated_physmap));
+
+               gnttab_set_unmap_op(&unmap[count], virt_to_machine(ptep), 
+                                   GNTMAP_host_map 
+                                   | GNTMAP_application_map 
+                                   | GNTMAP_contains_pte,
+                                   khandle->user);
+               count++;
+       }
+
+       if (count) {
+               int ret;
+
+               BLKTAP_INVALIDATE_HANDLE(khandle);
+
+               ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
+                                               unmap, count);
+               BUG_ON(ret);
+       }
+
+       return copy;
+}
+
 struct vm_operations_struct blktap_vm_ops = {
        nopage:   blktap_nopage,
+       zap_pte:    blktap_clear_pte,
 };
 
 /******************************************************************
@@ -604,6 +700,10 @@ static int blktap_mmap(struct file *filp
        vma->vm_private_data = map;
        vma->vm_flags |= VM_FOREIGN;
        vma->vm_flags |= VM_DONTCOPY;
+
+#ifdef CONFIG_X86
+       vma->vm_mm->context.has_foreign_mappings = 1;
+#endif
 
        info->vma = vma;
        info->ring_ok = 1;

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