Example memory map (from HP sx1000 with VGA enabled):
0x00000 - 0x9FFFF supports only WB (cacheable) access
0xA0000 - 0xBFFFF supports only UC (uncacheable) access
0xC0000 - 0xFFFFF supports only WB (cacheable) access
pci_read_rom() indirectly uses ioremap(0xC0000) to read the shadow VGA option
ROM. ioremap() used to default to a 16MB or 64MB UC kernel identity mapping,
which would cause an MCA when reading 0xC0000 since only WB is supported there.
X uses reads the option ROM to initialize devices. A smaller test case is:
# echo 1 > /sys/bus/pci/devices/0000:aa:03.0/rom
# cp /sys/bus/pci/devices/0000:aa:03.0/rom x
To avoid this, we can use the same ioremap_page_range() strategy that most
architectures use for all ioremaps. These page table mappings come out of the
vmalloc area. On ia64, these are in region 5 (0xA... addresses) and typically
use 16KB or 64KB mappings instead of 16MB or 64MB mappings. The smaller
mappings give more flexibility to use the correct attributes.
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@xxxxxx>
Index: work-mm10/arch/ia64/mm/ioremap.c
===================================================================
--- work-mm10.orig/arch/ia64/mm/ioremap.c 2007-03-20 21:03:33.000000000 -0700
+++ work-mm10/arch/ia64/mm/ioremap.c 2007-03-30 09:19:44.000000000 -0700
@@ -1,5 +1,5 @@
/*
- * (c) Copyright 2006 Hewlett-Packard Development Company, L.P.
+ * (c) Copyright 2006, 2007 Hewlett-Packard Development Company, L.P.
* Bjorn Helgaas <bjorn.helgaas@xxxxxx>
*
* This program is free software; you can redistribute it and/or modify
@@ -10,11 +10,13 @@
#include <linux/compiler.h>
#include <linux/module.h>
#include <linux/efi.h>
+#include <linux/io.h>
+#include <linux/vmalloc.h>
#include <asm/io.h>
#include <asm/meminit.h>
static inline void __iomem *
-__ioremap (unsigned long phys_addr, unsigned long size)
+__ioremap (unsigned long phys_addr)
{
return (void __iomem *) (__IA64_UNCACHED_OFFSET | phys_addr);
}
@@ -22,8 +24,13 @@
void __iomem *
ioremap (unsigned long phys_addr, unsigned long size)
{
+ void __iomem *addr;
+ struct vm_struct *area;
+ unsigned long offset;
+ pgprot_t prot;
u64 attr;
unsigned long gran_base, gran_size;
+ unsigned long page_base;
/*
* For things in kern_memmap, we must use the same attribute
@@ -34,7 +41,7 @@
if (attr & EFI_MEMORY_WB)
return (void __iomem *) phys_to_virt(phys_addr);
else if (attr & EFI_MEMORY_UC)
- return __ioremap(phys_addr, size);
+ return __ioremap(phys_addr);
/*
* Some chipsets don't support UC access to memory. If
@@ -45,7 +52,42 @@
if (efi_mem_attribute(gran_base, gran_size) & EFI_MEMORY_WB)
return (void __iomem *) phys_to_virt(phys_addr);
- return __ioremap(phys_addr, size);
+ /*
+ * WB is not supported for the whole granule, so we can't use
+ * the region 7 identity mapping. If we can safely cover the
+ * area with kernel page table mappings, we can use those
+ * instead.
+ */
+ page_base = phys_addr & PAGE_MASK;
+ size = PAGE_ALIGN(phys_addr + size) - page_base;
+ if (efi_mem_attribute(page_base, size) & EFI_MEMORY_WB) {
+ prot = PAGE_KERNEL;
+
+ /*
+ * Mappings have to be page-aligned
+ */
+ offset = phys_addr & ~PAGE_MASK;
+ phys_addr &= PAGE_MASK;
+
+ /*
+ * Ok, go for it..
+ */
+ area = get_vm_area(size, VM_IOREMAP);
+ if (!area)
+ return NULL;
+
+ area->phys_addr = phys_addr;
+ addr = (void __iomem *) area->addr;
+ if (ioremap_page_range((unsigned long) addr,
+ (unsigned long) addr + size, phys_addr, prot)) {
+ vunmap((void __force *) addr);
+ return NULL;
+ }
+
+ return (void __iomem *) (offset + (char __iomem *)addr);
+ }
+
+ return __ioremap(phys_addr);
}
EXPORT_SYMBOL(ioremap);
@@ -55,6 +97,14 @@
if (kern_mem_attribute(phys_addr, size) & EFI_MEMORY_WB)
return NULL;
- return __ioremap(phys_addr, size);
+ return __ioremap(phys_addr);
}
EXPORT_SYMBOL(ioremap_nocache);
+
+void
+iounmap (volatile void __iomem *addr)
+{
+ if (REGION_NUMBER(addr) == RGN_GATE)
+ vunmap((void *) ((unsigned long) addr & PAGE_MASK));
+}
+EXPORT_SYMBOL(iounmap);
Index: work-mm10/include/asm-ia64/io.h
===================================================================
--- work-mm10.orig/include/asm-ia64/io.h 2007-03-20 20:39:59.000000000 -0700
+++ work-mm10/include/asm-ia64/io.h 2007-03-20 21:03:34.000000000 -0700
@@ -421,11 +421,7 @@
extern void __iomem * ioremap(unsigned long offset, unsigned long size);
extern void __iomem * ioremap_nocache (unsigned long offset, unsigned long size);
-
-static inline void
-iounmap (volatile void __iomem *addr)
-{
-}
+extern void iounmap (volatile void __iomem *addr);
/* Use normal IO mappings for DMI */
#define dmi_ioremap ioremap
-
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