[PATCH] x86: let 'reservetop' functioning right

[Liang Li]

When specify 'reservetop=0xbadc0de' kernel parameter, the kernel will
stop booting due to a early_ioremap bug that relate to commit 8827247ff.

The root cause of boot failure problem is the value of 'slot_virt[i]'
was initialized in setup_arch->early_ioremap_init. But later in
setup_arch, the function 'parse_early_param' will modify 'FIXADDR_TOP'
when 'reservetop=0xbadc0de' being specified.

When reservetop being handled then FIXADDR_TOP get adjusted, Hence check
prev_map then re-initialize slot_virt and PMD based on new FIXADDR_TOP.

Signed-off-by: Liang Li <liang.li@xxxxxxxxxxxxx>
Cc: Wang Chen <wangchen@xxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/io.h |    1 +
 arch/x86/mm/ioremap.c     |   15 +++++++++++++++
 arch/x86/mm/pgtable.c     |    2 ++
 3 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index a1dcfa3..30a3e97 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -347,6 +347,7 @@ extern void __iomem *early_ioremap(resource_size_t phys_addr,
 extern void __iomem *early_memremap(resource_size_t phys_addr,
 				    unsigned long size);
 extern void early_iounmap(void __iomem *addr, unsigned long size);
+extern void fixup_early_ioremap(void);
 
 #define IO_SPACE_LIMIT 0xffff
 
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 5eb1ba7..e4ab706 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -448,6 +448,21 @@ static inline void __init early_clear_fixmap(enum fixed_addresses idx)
 static void __iomem *prev_map[FIX_BTMAPS_SLOTS] __initdata;
 static unsigned long prev_size[FIX_BTMAPS_SLOTS] __initdata;
 
+void __init fixup_early_ioremap(void)
+{
+	int i;
+	for (i = 0; i < FIX_BTMAPS_SLOTS; i++) {
+		if (prev_map[i])
+			break;
+	}
+
+	if (i < FIX_BTMAPS_SLOTS)
+		BUG_ON(1);
+
+	early_ioremap_init();
+	return;
+}
+
 static int __init check_early_ioremap_leak(void)
 {
 	int count = 0;
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 5c4ee42..ea4d54c 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -4,6 +4,7 @@
 #include <asm/pgtable.h>
 #include <asm/tlb.h>
 #include <asm/fixmap.h>
+#include <asm/io.h>
 
 #define PGALLOC_GFP GFP_KERNEL | __GFP_NOTRACK | __GFP_REPEAT | __GFP_ZERO
 
@@ -351,6 +352,7 @@ void __init reserve_top_address(unsigned long reserve)
 	printk(KERN_INFO "Reserving virtual address space above 0x%08x\n",
 	       (int)-reserve);
 	__FIXADDR_TOP = -reserve - PAGE_SIZE;
+	fixup_early_ioremap();
 #endif
 }
 
-----------
Acceptable?

Thanks and regards,
	   -Liang Li
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