Commit 38cb47ba authored Feb 04, 2008 by Ingo Molnar

x86: relax RAM check in ioremap()



Kevin Winchester reported the loss of direct rendering, due to:

[    0.588184] agpgart: Detected AGP bridge 0
[    0.588184] agpgart: unable to get memory for graphics translation table.
[    0.588184] agpgart: agp_backend_initialize() failed.
[    0.588207] agpgart-amd64: probe of 0000:00:00.0 failed with error -12

and bisected it down to:

  commit 266b9f87
  Author: Thomas Gleixner <tglx@linutronix.de>
  Date:   Wed Jan 30 13:34:06 2008 +0100

      x86: fix ioremap RAM check

this check was too strict and caused an ioremap() failure.

the problem is due to the somewhat unclean way of how the GART code
reserves a memory range for its aperture, and how it utilizes it
later on.

Allow RAM pages to be ioremap()-ed too, as long as they are reserved.

Bisected-by: Kevin Winchester <kjwinchester@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Tested-by: Kevin Winchester <kjwinchester@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent 9135f190

arch/x86/mm/ioremap.c

+5 −4

Original line number	Diff line number	Diff line
		@@ -116,7 +116,7 @@ static void __iomem *__ioremap(unsigned long phys_addr, unsigned long size,
		{
		void __iomem *addr;
		struct vm_struct *area;
		unsigned long offset, last_addr;
		unsigned long pfn, offset, last_addr;
		pgprot_t prot;

		/* Don't allow wraparound or zero size */
		@@ -133,9 +133,10 @@ static void __iomem *__ioremap(unsigned long phys_addr, unsigned long size,
		/*
		* Don't allow anybody to remap normal RAM that we're using..
		*/
		for (offset = phys_addr >> PAGE_SHIFT; offset < max_pfn_mapped &&
		(offset << PAGE_SHIFT) < last_addr; offset++) {
		if (page_is_ram(offset))
		for (pfn = phys_addr >> PAGE_SHIFT; pfn < max_pfn_mapped &&
		(pfn << PAGE_SHIFT) < last_addr; pfn++) {
		if (page_is_ram(pfn) && pfn_valid(pfn) &&
		!PageReserved(pfn_to_page(pfn)))
		return NULL;
		}

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