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Re: [Xen-devel] [PATCH v2 1/2] xen/grant-table: Avoid m2p_override during mapping
- To: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, David Vrabel <david.vrabel@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, <x86@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>, <linux-kernel@xxxxxxxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxx>
- From: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>
- Date: Sat, 18 Jan 2014 21:01:37 +0000
- Cc: Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>
- Delivery-date: Sat, 18 Jan 2014 21:02:26 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
On 13/01/14 19:08, Zoltan Kiss wrote:
@@ -284,8 +287,37 @@ static int map_grant_pages(struct grant_map *map)
}
pr_debug("map %d+%d\n", map->index, map->count);
- err = gnttab_map_refs(map->map_ops, use_ptemod ? map->kmap_ops : NULL,
- map->pages, map->count);
+ err = gnttab_map_refs(map->map_ops, NULL, map->pages, map->count);
+ if (err)
+ return err;
+
+ if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
+ arch_enter_lazy_mmu_mode();
+ lazy = true;
+ }
+
+ for (i = 0; i < map->count; i++) {
+ /* Do not add to override if the map failed. */
+ if (map->map_ops[i].status)
+ continue;
+
+ if (map->map_ops[i].flags & GNTMAP_contains_pte) {
+ pte = (pte_t *)
(mfn_to_virt(PFN_DOWN(map->map_ops[i].host_addr)) +
+ (map->map_ops[i].host_addr & ~PAGE_MASK));
+ mfn = pte_mfn(*pte);
+ } else {
+ mfn = PFN_DOWN(map->map_ops[i].dev_bus_addr);
+ }
+ err = m2p_add_override(mfn,
+ map->pages[i],
+ use_ptemod ? &map->kmap_ops[i] : NULL);
+ if (err)
+ break;
+ }
+
+ if (lazy)
+ arch_leave_lazy_mmu_mode();
+
if (err)
return err;
This patch has a fundamental problem here: we change the pfn in
gnttab_map_refs, then fetch it in m2p_override again, but then we have a
different one than we need. This causes Dom0 crash. I will send a new
version to fix that.
Zoli
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