mm: provide early_memremap_ro to establish read-only mapping

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>
Acked-by: Konrad Rzeszutek Wilk <Konrad.wilk@oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

diff --git a/include/asm-generic/early_ioremap.h b/include/asm-generic/early_ioremap.h
index a5de55c04fb2ee56b8f77a3444028aa52c3ecbb9..316bd043319ebaf36dc1a7d33e1cb18ce0490b0e 100644 (file)
--- 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 f23174fb9ec4340378df59b5cc89b43ecf342bec..1cbb8338edf391bd83c4d1b0bc0dff2cbbe56e75 100644 (file)
--- 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
+#if !defined(FIXMAP_PAGE_RO) && defined(PAGE_KERNEL_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 e10ccd299d6666887ba9347308afaa112ee8816f..0cfadafb3fb00bd9cccb373449857443c443f3a6 100644 (file)
--- a/mm/early_ioremap.c
+++ b/mm/early_ioremap.c
@@ -217,6 +217,13 @@ early_memremap(resource_size_t phys_addr, unsigned long size)
        return (__force void *)__early_ioremap(phys_addr, size,
                                               FIXMAP_PAGE_NORMAL);
 }
+#ifdef FIXMAP_PAGE_RO
+void __init *
+early_memremap_ro(resource_size_t phys_addr, unsigned long size)
+{
+       return (__force void *)__early_ioremap(phys_addr, size, FIXMAP_PAGE_RO);
+}
+#endif
 #else /* CONFIG_MMU */
 
 void __init __iomem *
@@ -231,6 +238,11 @@ 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)
 {