On Fri, Jan 21, 2011 at 10:59:06AM -0500, Daniel De Graaf wrote:
> HVM does not allow direct PTE modification, so instead we request
> that Xen change its internal p2m mappings on the allocated pages and
> map the memory into userspace normally.
>
> Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
> ---
> drivers/xen/gntdev.c | 115 +++++++++++++++++++++++++++++++-------------
> drivers/xen/grant-table.c | 6 ++
> 2 files changed, 87 insertions(+), 34 deletions(-)
>
> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> index 256162b..a5710e8 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -32,6 +32,7 @@
> #include <linux/sched.h>
> #include <linux/spinlock.h>
> #include <linux/slab.h>
> +#include <linux/highmem.h>
>
> #include <xen/xen.h>
> #include <xen/grant_table.h>
> @@ -52,6 +53,8 @@ MODULE_PARM_DESC(limit, "Maximum number of grants that may
> be mapped by "
>
> static atomic_t pages_mapped = ATOMIC_INIT(0);
>
> +static int use_ptemod;
> +
> struct gntdev_priv {
> struct list_head maps;
> /* lock protects maps from concurrent changes */
> @@ -74,6 +77,8 @@ struct grant_map {
> struct page **pages;
> };
>
> +static int unmap_grant_pages(struct grant_map *map, int offset, int pages);
> +
> /* ------------------------------------------------------------------ */
>
> static void gntdev_print_maps(struct gntdev_priv *priv,
> @@ -179,11 +184,32 @@ static void gntdev_put_map(struct grant_map *map)
>
> atomic_sub(map->count, &pages_mapped);
>
> - if (map->pages)
> + if (map->pages) {
> + if (!use_ptemod)
> + unmap_grant_pages(map, 0, map->count);
> +
> for (i = 0; i < map->count; i++) {
> - if (map->pages[i])
> + uint32_t check, *tmp;
> + if (!map->pages[i])
> + continue;
> + /* XXX When unmapping in an HVM domain, Xen will
> + * sometimes end up mapping the GFN to an invalid MFN.
> + * In this case, writes will be discarded and reads will
> + * return all 0xFF bytes. Leak these unusable GFNs
I forgot to ask, under what version of Xen did you run this? I want to add
that to the comment so when it gets fixed we know what the failing version is.
> + * until Xen supports fixing their p2m mapping.
> + */
> + tmp = kmap(map->pages[i]);
> + *tmp = 0xdeaddead;
> + mb();
> + check = *tmp;
> + kunmap(map->pages[i]);
> + if (check == 0xdeaddead)
> __free_page(map->pages[i]);
> + else
> + pr_debug("Discard page %d=%ld\n", i,
> + page_to_pfn(map->pages[i]));
> }
> + }
> kfree(map->pages);
> kfree(map->grants);
> kfree(map->map_ops);
> @@ -198,17 +224,16 @@ static int find_grant_ptes(pte_t *pte, pgtable_t token,
> {
> struct grant_map *map = data;
> unsigned int pgnr = (addr - map->vma->vm_start) >> PAGE_SHIFT;
> + int flags = map->flags | GNTMAP_application_map | GNTMAP_contains_pte;
> u64 pte_maddr;
>
> BUG_ON(pgnr >= map->count);
> pte_maddr = arbitrary_virt_to_machine(pte).maddr;
>
> - gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr,
> - GNTMAP_contains_pte | map->flags,
> + gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr, flags,
> map->grants[pgnr].ref,
> map->grants[pgnr].domid);
> - gnttab_set_unmap_op(&map->unmap_ops[pgnr], pte_maddr,
> - GNTMAP_contains_pte | map->flags,
> + gnttab_set_unmap_op(&map->unmap_ops[pgnr], pte_maddr, flags,
> 0 /* handle */);
> return 0;
> }
> @@ -216,6 +241,19 @@ static int find_grant_ptes(pte_t *pte, pgtable_t token,
> static int map_grant_pages(struct grant_map *map)
> {
> int i, err = 0;
> + phys_addr_t addr;
> +
> + if (!use_ptemod) {
> + for (i = 0; i < map->count; i++) {
> + addr = (phys_addr_t)
> + pfn_to_kaddr(page_to_pfn(map->pages[i]));
> + gnttab_set_map_op(&map->map_ops[i], addr, map->flags,
> + map->grants[i].ref,
> + map->grants[i].domid);
> + gnttab_set_unmap_op(&map->unmap_ops[i], addr,
> + map->flags, 0 /* handle */);
> + }
> + }
>
> pr_debug("map %d+%d\n", map->index, map->count);
> err = gnttab_map_refs(map->map_ops, map->pages, map->count);
> @@ -260,17 +298,8 @@ static void gntdev_vma_close(struct vm_area_struct *vma)
> gntdev_put_map(map);
> }
>
> -static int gntdev_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> -{
> - pr_debug("vaddr %p, pgoff %ld (shouldn't happen)\n",
> - vmf->virtual_address, vmf->pgoff);
> - vmf->flags = VM_FAULT_ERROR;
> - return 0;
> -}
> -
> static struct vm_operations_struct gntdev_vmops = {
> .close = gntdev_vma_close,
> - .fault = gntdev_vma_fault,
> };
>
> /* ------------------------------------------------------------------ */
> @@ -355,14 +384,16 @@ static int gntdev_open(struct inode *inode, struct file
> *flip)
> INIT_LIST_HEAD(&priv->maps);
> spin_lock_init(&priv->lock);
>
> - priv->mm = get_task_mm(current);
> - if (!priv->mm) {
> - kfree(priv);
> - return -ENOMEM;
> + if (use_ptemod) {
> + priv->mm = get_task_mm(current);
> + if (!priv->mm) {
> + kfree(priv);
> + return -ENOMEM;
> + }
> + priv->mn.ops = &gntdev_mmu_ops;
> + ret = mmu_notifier_register(&priv->mn, priv->mm);
> + mmput(priv->mm);
> }
> - priv->mn.ops = &gntdev_mmu_ops;
> - ret = mmu_notifier_register(&priv->mn, priv->mm);
> - mmput(priv->mm);
>
> if (ret) {
> kfree(priv);
> @@ -390,7 +421,8 @@ static int gntdev_release(struct inode *inode, struct
> file *flip)
> }
> spin_unlock(&priv->lock);
>
> - mmu_notifier_unregister(&priv->mn, priv->mm);
> + if (use_ptemod)
> + mmu_notifier_unregister(&priv->mn, priv->mm);
> kfree(priv);
> return 0;
> }
> @@ -515,7 +547,7 @@ static int gntdev_mmap(struct file *flip, struct
> vm_area_struct *vma)
> int index = vma->vm_pgoff;
> int count = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
> struct grant_map *map;
> - int err = -EINVAL;
> + int i, err = -EINVAL;
>
> if ((vma->vm_flags & VM_WRITE) && !(vma->vm_flags & VM_SHARED))
> return -EINVAL;
> @@ -527,9 +559,9 @@ static int gntdev_mmap(struct file *flip, struct
> vm_area_struct *vma)
> map = gntdev_find_map_index(priv, index, count);
> if (!map)
> goto unlock_out;
> - if (map->vma)
> + if (use_ptemod && map->vma)
> goto unlock_out;
> - if (priv->mm != vma->vm_mm) {
> + if (use_ptemod && priv->mm != vma->vm_mm) {
> printk(KERN_WARNING "Huh? Other mm?\n");
> goto unlock_out;
> }
> @@ -541,20 +573,24 @@ static int gntdev_mmap(struct file *flip, struct
> vm_area_struct *vma)
> vma->vm_flags |= VM_RESERVED|VM_DONTCOPY|VM_DONTEXPAND|VM_PFNMAP;
>
> vma->vm_private_data = map;
> - map->vma = vma;
>
> - map->flags = GNTMAP_host_map | GNTMAP_application_map;
> + if (use_ptemod)
> + map->vma = vma;
> +
> + map->flags = GNTMAP_host_map;
> if (!(vma->vm_flags & VM_WRITE))
> map->flags |= GNTMAP_readonly;
>
> spin_unlock(&priv->lock);
>
> - err = apply_to_page_range(vma->vm_mm, vma->vm_start,
> - vma->vm_end - vma->vm_start,
> - find_grant_ptes, map);
> - if (err) {
> - printk(KERN_WARNING "find_grant_ptes() failure.\n");
> - return err;
> + if (use_ptemod) {
> + err = apply_to_page_range(vma->vm_mm, vma->vm_start,
> + vma->vm_end - vma->vm_start,
> + find_grant_ptes, map);
> + if (err) {
> + printk(KERN_WARNING "find_grant_ptes() failure.\n");
> + return err;
> + }
> }
>
> err = map_grant_pages(map);
> @@ -565,6 +601,15 @@ static int gntdev_mmap(struct file *flip, struct
> vm_area_struct *vma)
>
> map->is_mapped = 1;
>
> + if (!use_ptemod) {
> + for (i = 0; i < count; i++) {
> + err = vm_insert_page(vma, vma->vm_start + i*PAGE_SIZE,
> + map->pages[i]);
> + if (err)
> + return err;
> + }
> + }
> +
> return 0;
>
> unlock_out:
> @@ -595,6 +640,8 @@ static int __init gntdev_init(void)
> if (!xen_domain())
> return -ENODEV;
>
> + use_ptemod = xen_pv_domain();
> +
> err = misc_register(&gntdev_miscdev);
> if (err != 0) {
> printk(KERN_ERR "Could not register gntdev device\n");
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index 9ef54eb..9428ced 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -458,6 +458,9 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
> if (ret)
> return ret;
>
> + if (xen_feature(XENFEAT_auto_translated_physmap))
> + return ret;
> +
> for (i = 0; i < count; i++) {
> /* m2p override only supported for GNTMAP_contains_pte mappings
> */
> if (!(map_ops[i].flags & GNTMAP_contains_pte))
> @@ -483,6 +486,9 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref
> *unmap_ops,
> if (ret)
> return ret;
>
> + if (xen_feature(XENFEAT_auto_translated_physmap))
> + return ret;
> +
> for (i = 0; i < count; i++) {
> ret = m2p_remove_override(pages[i]);
> if (ret)
> --
> 1.7.3.4
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