return ret;
}
+#ifdef CONFIG_X86_64
+static __initdata u64 __last_pgt_set_rw = 0;
+static __initdata u64 __pgt_buf_start = 0;
+static __initdata u64 __pgt_buf_end = 0;
+static __initdata u64 __pgt_buf_top = 0;
+/*
+ * As a consequence of the commit:
+ *
+ * commit 4b239f458c229de044d6905c2b0f9fe16ed9e01e
+ * Author: Yinghai Lu <yinghai@kernel.org>
+ * Date: Fri Dec 17 16:58:28 2010 -0800
+ *
+ * x86-64, mm: Put early page table high
+ *
+ * at some point init_memory_mapping is going to reach the pagetable pages
+ * area and map those pages too (mapping them as normal memory that falls
+ * in the range of addresses passed to init_memory_mapping as argument).
+ * Some of those pages are already pagetable pages (they are in the range
+ * pgt_buf_start-pgt_buf_end) therefore they are going to be mapped RO and
+ * everything is fine.
+ * Some of these pages are not pagetable pages yet (they fall in the range
+ * pgt_buf_end-pgt_buf_top; for example the page at pgt_buf_end) so they
+ * are going to be mapped RW. When these pages become pagetable pages and
+ * are hooked into the pagetable, xen will find that the guest has already
+ * a RW mapping of them somewhere and fail the operation.
+ * The reason Xen requires pagetables to be RO is that the hypervisor needs
+ * to verify that the pagetables are valid before using them. The validation
+ * operations are called "pinning".
+ *
+ * In order to fix the issue we mark all the pages in the entire range
+ * pgt_buf_start-pgt_buf_top as RO, however when the pagetable allocation
+ * is completed only the range pgt_buf_start-pgt_buf_end is reserved by
+ * init_memory_mapping. Hence the kernel is going to crash as soon as one
+ * of the pages in the range pgt_buf_end-pgt_buf_top is reused (b/c those
+ * ranges are RO).
+ *
+ * For this reason, 'mark_rw_past_pgt' is introduced which is called _after_
+ * the init_memory_mapping has completed (in a perfect world we would
+ * call this function from init_memory_mapping, but lets ignore that).
+ *
+ * Because we are called _after_ init_memory_mapping the pgt_buf_[start,
+ * end,top] have all changed to new values (b/c init_memory_mapping
+ * is called and setting up another new page-table). Hence, the first time
+ * we enter this function, we save away the pgt_buf_start value and update
+ * the pgt_buf_[end,top].
+ *
+ * When we detect that the "old" pgt_buf_start through pgt_buf_end
+ * PFNs have been reserved (so memblock_x86_reserve_range has been called),
+ * we immediately set out to RW the "old" pgt_buf_end through pgt_buf_top.
+ *
+ * And then we update those "old" pgt_buf_[end|top] with the new ones
+ * so that we can redo this on the next pagetable.
+ */
+static __init void mark_rw_past_pgt(void) {
+
+ if (pgt_buf_end > pgt_buf_start) {
+ u64 addr, size;
+
+ /* Save it away. */
+ if (!__pgt_buf_start) {
+ __pgt_buf_start = pgt_buf_start;
+ __pgt_buf_end = pgt_buf_end;
+ __pgt_buf_top = pgt_buf_top;
+ return;
+ }
+ /* If we get the range that starts at __pgt_buf_end that means
+ * the range is reserved, and that in 'init_memory_mapping'
+ * the 'memblock_x86_reserve_range' has been called with the
+ * outdated __pgt_buf_start, __pgt_buf_end (the "new"
+ * pgt_buf_[start|end|top] refer now to a new pagetable.
+ * Note: we are called _after_ the pgt_buf_[..] have been
+ * updated.*/
+
+ addr = memblock_x86_find_in_range_size(PFN_PHYS(__pgt_buf_start),
+ &size, PAGE_SIZE);
+
+ /* Still not reserved, meaning 'memblock_x86_reserve_range'
+ * hasn't been called yet. Update the _end and _top.*/
+ if (addr == PFN_PHYS(__pgt_buf_start)) {
+ __pgt_buf_end = pgt_buf_end;
+ __pgt_buf_top = pgt_buf_top;
+ return;
+ }
+
+ /* OK, the area is reserved, meaning it is time for us to
+ * set RW for the old end->top PFNs. */
+
+ /* ..unless we had already done this. */
+ if (__pgt_buf_end == __last_pgt_set_rw)
+ return;
+
+ addr = PFN_PHYS(__pgt_buf_end);
+
+ /* set as RW the rest */
+ printk(KERN_DEBUG "xen: setting RW the range %llx - %llx\n",
+ PFN_PHYS(__pgt_buf_end), PFN_PHYS(__pgt_buf_top));
+
+ while (addr < PFN_PHYS(__pgt_buf_top)) {
+ make_lowmem_page_readwrite(__va(addr));
+ addr += PAGE_SIZE;
+ }
+ /* And update everything so that we are ready for the next
+ * pagetable (the one created for regions past 4GB) */
+ __last_pgt_set_rw = __pgt_buf_end;
+ __pgt_buf_start = pgt_buf_start;
+ __pgt_buf_end = pgt_buf_end;
+ __pgt_buf_top = pgt_buf_top;
+ }
+ return;
+}
+#else
+static __init void mark_rw_past_pgt(void) { }
+#endif
static void xen_pgd_free(struct mm_struct *mm, pgd_t *pgd)
{
#ifdef CONFIG_X86_64
{
unsigned long pfn = pte_pfn(pte);
+ /*
+ * A bit of optimization. We do not need to call the workaround
+ * when xen_set_pte_init is called with a PTE with 0 as PFN.
+ * That is b/c the pagetable at that point are just being populated
+ * with empty values and we can save some cycles by not calling
+ * the 'memblock' code.*/
+ if (pfn)
+ mark_rw_past_pgt();
/*
* If the new pfn is within the range of the newly allocated
* kernel pagetable, and it isn't being mapped into an
static __init void xen_post_allocator_init(void)
{
+ mark_rw_past_pgt();
+
#ifdef CONFIG_XEN_DEBUG
pv_mmu_ops.make_pte = PV_CALLEE_SAVE(xen_make_pte_debug);
#endif
projects / mirror_ubuntu-kernels.git / commitdiff