xen/mmu: Remove from __ka space PMD entries for pagetables.

Please first read the description in "xen/mmu: Copy and revector the
P2M tree."

At this stage, the __ka address space (which is what the old
P2M tree was using) is partially disassembled. The cleanup_highmap
has removed the PMD entries from 0-16MB and anything past _brk_end
up to the max_pfn_mapped (which is the end of the ramdisk).

The xen_remove_p2m_tree and code around has ripped out the __ka for
the old P2M array.

Here we continue on doing it to where the Xen page-tables were.
It is safe to do it, as the page-tables are addressed using __va.
For good measure we delete anything that is within MODULES_VADDR
and up to the end of the PMD.

At this point the __ka only contains PMD entries for the start
of the kernel up to __brk.

[v1: Per Stefano's suggestion wrapped the MODULES_VADDR in debug]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index a640949f78d4..3f8e963b76c0 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1240,6 +1240,25 @@ static void __init xen_pagetable_setup_done(pgd_t *base)
                         xen_start_info->mfn_list = new_mfn_list;
                 }
         }
+        /* At this stage, cleanup_highmap has already cleaned __ka space
+         * from _brk_limit way up to the max_pfn_mapped (which is the end of
+         * the ramdisk). We continue on, erasing PMD entries that point to page
+         * tables - do note that they are accessible at this stage via __va.
+         * For good measure we also round up to the PMD - which means that if
+         * anybody is using __ka address to the initial boot-stack - and try
+         * to use it - they are going to crash. The xen_start_info has been
+         * taken care of already in xen_setup_kernel_pagetable. */
+        addr = xen_start_info->pt_base;
+        size = roundup(xen_start_info->nr_pt_frames * PAGE_SIZE, PMD_SIZE);
+
+        xen_cleanhighmap(addr, addr + size);
+        xen_start_info->pt_base = (unsigned long)__va(__pa(xen_start_info->pt_base));
+#ifdef DEBUG
+        /* This is superflous and is not neccessary, but you know what
+         * lets do it. The MODULES_VADDR -> MODULES_END should be clear of
+         * anything at this stage. */
+        xen_cleanhighmap(MODULES_VADDR, roundup(MODULES_VADDR, PUD_SIZE) - 1);
+#endif
 #endif
         xen_post_allocator_init();
 }