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[Patch V4 12/16] mm: provide early_memremap_ro to establish read-only mapping

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During early boot as Xen pv domain the kernel needs to map some page
tables supplied by the hypervisor read only. This is needed to be
able to relocate some data structures conflicting with the physical
memory map especially on systems with huge RAM (above 512GB).

Provide the function early_memremap_ro() to provide this read only
mapping.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 include/asm-generic/early_ioremap.h |  2 ++
 include/asm-generic/fixmap.h        |  3 +++
 mm/early_ioremap.c                  | 11 +++++++++++
 3 files changed, 16 insertions(+)

diff --git a/include/asm-generic/early_ioremap.h b/include/asm-generic/early_ioremap.h
index a5de55c..316bd04 100644
--- a/include/asm-generic/early_ioremap.h
+++ b/include/asm-generic/early_ioremap.h
@@ -11,6 +11,8 @@ extern void __iomem *early_ioremap(resource_size_t phys_addr,
 				   unsigned long size);
 extern void *early_memremap(resource_size_t phys_addr,
 			    unsigned long size);
+extern void *early_memremap_ro(resource_size_t phys_addr,
+			       unsigned long size);
 extern void early_iounmap(void __iomem *addr, unsigned long size);
 extern void early_memunmap(void *addr, unsigned long size);
 
diff --git a/include/asm-generic/fixmap.h b/include/asm-generic/fixmap.h
index f23174f..d8cc637 100644
--- a/include/asm-generic/fixmap.h
+++ b/include/asm-generic/fixmap.h
@@ -46,6 +46,9 @@ static inline unsigned long virt_to_fix(const unsigned long vaddr)
 #ifndef FIXMAP_PAGE_NORMAL
 #define FIXMAP_PAGE_NORMAL PAGE_KERNEL
 #endif
+#ifndef FIXMAP_PAGE_RO
+#define FIXMAP_PAGE_RO PAGE_KERNEL_RO
+#endif
 #ifndef FIXMAP_PAGE_NOCACHE
 #define FIXMAP_PAGE_NOCACHE PAGE_KERNEL_NOCACHE
 #endif
diff --git a/mm/early_ioremap.c b/mm/early_ioremap.c
index e10ccd2..e4ffaac 100644
--- a/mm/early_ioremap.c
+++ b/mm/early_ioremap.c
@@ -217,6 +217,12 @@ early_memremap(resource_size_t phys_addr, unsigned long size)
 	return (__force void *)__early_ioremap(phys_addr, size,
 					       FIXMAP_PAGE_NORMAL);
 }
+void __init *
+early_memremap_ro(resource_size_t phys_addr, unsigned long size)
+{
+	return (__force void *)__early_ioremap(phys_addr, size,
+					       FIXMAP_PAGE_RO);
+}
 #else /* CONFIG_MMU */
 
 void __init __iomem *
@@ -231,6 +237,11 @@ early_memremap(resource_size_t phys_addr, unsigned long size)
 {
 	return (void *)phys_addr;
 }
+void __init *
+early_memremap_ro(resource_size_t phys_addr, unsigned long size)
+{
+	return (void *)phys_addr;
+}
 
 void __init early_iounmap(void __iomem *addr, unsigned long size)
 {
-- 
2.1.4

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[Patch V4 00/16] xen: support pv-domains larger than 512GB Juergen Gross <jgross@suse.com> - 2015-06-08 14:10 +0200
  [Patch V4 06/16] xen: split counting of extra memory pages from remapping Juergen Gross <jgross@suse.com> - 2015-06-08 14:10 +0200
  [Patch V4 11/16] xen: check for initrd conflicting with e820 map Juergen Gross <jgross@suse.com> - 2015-06-08 14:10 +0200
  [Patch V4 09/16] xen: check for kernel memory conflicting with memory layout Juergen Gross <jgross@suse.com> - 2015-06-08 14:10 +0200
  [Patch V4 01/16] xen: sync with xen headers Juergen Gross <jgross@suse.com> - 2015-06-08 14:10 +0200
  [Patch V4 16/16] xen: remove no longer needed p2m.h Juergen Gross <jgross@suse.com> - 2015-06-08 14:10 +0200
  [Patch V4 14/16] xen: move p2m list if conflicting with e820 map Juergen Gross <jgross@suse.com> - 2015-06-08 14:10 +0200
    Re: [Xen-devel] [Patch V4 14/16] xen: move p2m list if conflicting  with e820 map David Vrabel <david.vrabel@citrix.com> - 2015-06-11 13:10 +0200
  [Patch V4 07/16] xen: check memory area against e820 map Juergen Gross <jgross@suse.com> - 2015-06-08 14:10 +0200
  [Patch V4 10/16] xen: check pre-allocated page tables for conflict with memory map Juergen Gross <jgross@suse.com> - 2015-06-08 14:10 +0200
  [Patch V4 15/16] xen: allow more than 512 GB of RAM for 64 bit pv-domains Juergen Gross <jgross@suse.com> - 2015-06-08 14:10 +0200
  [Patch V4 02/16] xen: save linear p2m list address in shared info structure Juergen Gross <jgross@suse.com> - 2015-06-08 14:10 +0200
  [Patch V4 08/16] xen: find unused contiguous memory area Juergen Gross <jgross@suse.com> - 2015-06-08 14:10 +0200
  [Patch V4 13/16] xen: add explicit memblock_reserve() calls for special pages Juergen Gross <jgross@suse.com> - 2015-06-08 14:10 +0200
  [Patch V4 12/16] mm: provide early_memremap_ro to establish read-only mapping Juergen Gross <jgross@suse.com> - 2015-06-08 14:10 +0200

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