Re: [PATCH 1/2] cleanup e820_setup_gap

[Alok Kataria]

On Fri, 2008-06-20 at 12:50 -0700, Yinghai Lu wrote:
> On Fri, Jun 20, 2008 at 12:38 PM, Alok Kataria <akataria@xxxxxxxxxx> wrote:
> > Here is the patch based on tip/master
> >
> > Please have a look
> >
> > --
> >
> > This is a preparatory patch for the next patch in series.
> > Moves some code from e820_setup_gap to a new function e820_search_gap.
> > This patch is a part of a bug fix where we walk the ACPI table to calculate
> > a gap for PCI optional devices.
> >
> > Signed-off-by: Alok N Kataria <akataria@xxxxxxxxxx>
> >
> > Index: linux-trees.git/arch/x86/kernel/e820.c
> > ===================================================================
> > --- linux-trees.git.orig/arch/x86/kernel/e820.c 2008-06-20 10:32:44.000000000 -0700
> > +++ linux-trees.git/arch/x86/kernel/e820.c      2008-06-20 12:27:58.000000000 -0700
> > @@ -442,26 +442,22 @@
> >  }
> >
> >  /*
> > - * Search for the biggest gap in the low 32 bits of the e820
> > - * memory space.  We pass this space to PCI to assign MMIO resources
> > - * for hotplug or unconfigured devices in.
> > - * Hopefully the BIOS let enough space left.
> > + * Search for a gap in the e820 memory space from start_addr to 2^32.
> >  */
> > -__init void e820_setup_gap(void)
> > +__init int e820_search_gap(unsigned long *gapstart, unsigned long *gapsize,
> > +               unsigned long start_addr)
> >  {
> > -       unsigned long gapstart, gapsize, round;
> > -       unsigned long long last;
> > -       int i;
> > +       unsigned long last = 0x100000000ull;
> 
> why changing "unsigned long long" to "unsigned long" ?
> it will overflow on 32bit
> 

Oops...my bad, it was unsigned long in e820_64.c. Should be more careful
with these cross ports.
Thanks for catching it.
--

This is a preparatory patch for the next patch in series.
Moves some code from e820_setup_gap to a new function e820_search_gap.
This patch is a part of a bug fix where we walk the ACPI table to calculate
a gap for PCI optional devices.

Signed-off-by: Alok N Kataria <akataria@xxxxxxxxxx>

Index: linux-trees.git/arch/x86/kernel/e820.c
===================================================================
--- linux-trees.git.orig/arch/x86/kernel/e820.c	2008-06-20 10:32:44.000000000 -0700
+++ linux-trees.git/arch/x86/kernel/e820.c	2008-06-20 13:23:32.000000000 -0700
@@ -442,26 +442,22 @@
 }
 
 /*
- * Search for the biggest gap in the low 32 bits of the e820
- * memory space.  We pass this space to PCI to assign MMIO resources
- * for hotplug or unconfigured devices in.
- * Hopefully the BIOS let enough space left.
+ * Search for a gap in the e820 memory space from start_addr to 2^32.
  */
-__init void e820_setup_gap(void)
+__init int e820_search_gap(unsigned long *gapstart, unsigned long *gapsize,
+		unsigned long start_addr)
 {
-	unsigned long gapstart, gapsize, round;
-	unsigned long long last;
-	int i;
+	unsigned long long last = 0x100000000ull;
+	int i = e820.nr_map;
 	int found = 0;
 
-	last = 0x100000000ull;
-	gapstart = 0x10000000;
-	gapsize = 0x400000;
-	i = e820.nr_map;
 	while (--i >= 0) {
 		unsigned long long start = e820.map[i].addr;
 		unsigned long long end = start + e820.map[i].size;
 
+		if (end < start_addr)
+			continue;
+
 		/*
 		 * Since "last" is at most 4GB, we know we'll
 		 * fit in 32 bits if this condition is true
@@ -469,15 +465,32 @@
 		if (last > end) {
 			unsigned long gap = last - end;
 
-			if (gap > gapsize) {
-				gapsize = gap;
-				gapstart = end;
+			if (gap >= *gapsize) {
+				*gapsize = gap;
+				*gapstart = end;
 				found = 1;
 			}
 		}
 		if (start < last)
 			last = start;
 	}
+	return found;
+}
+
+/*
+ * Search for the biggest gap in the low 32 bits of the e820
+ * memory space.  We pass this space to PCI to assign MMIO resources
+ * for hotplug or unconfigured devices in.
+ * Hopefully the BIOS let enough space left.
+ */
+__init void e820_setup_gap(void)
+{
+	unsigned long gapstart, gapsize, round;
+	int found;
+
+	gapstart = 0x10000000;
+	gapsize = 0x400000;
+	found  = e820_search_gap(&gapstart, &gapsize, 0);
 
 #ifdef CONFIG_X86_64
 	if (!found) {
Index: linux-trees.git/include/asm-x86/e820.h
===================================================================
--- linux-trees.git.orig/include/asm-x86/e820.h	2008-06-20 10:32:44.000000000 -0700
+++ linux-trees.git/include/asm-x86/e820.h	2008-06-20 12:18:40.000000000 -0700
@@ -69,6 +69,8 @@
 			       unsigned new_type);
 extern void update_e820(void);
 extern void e820_setup_gap(void);
+extern int e820_search_gap(unsigned long *gapstart, unsigned long *gapsize,
+				unsigned long start_addr);
 struct setup_data;
 extern void parse_e820_ext(struct setup_data *data, unsigned long pa_data);
 





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