[Xen-devel] [PATCH 6/6] xen/mmu: Remove from __ka space PMD entries for pagetables.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

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@xxxxxxxxxx>
---
 arch/x86/xen/mmu.c |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 9358b75..fa4d208 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 shouldn't be 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();
 }
-- 
1.7.7.6


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