[RFC 5/8] x86_64 without ZONE_DMA

Christoph Lameter
2006-07-08T00:06:01Z

x86_64: ZONE_DMA/ZONE_DMA32 optional

Allow the use to specify CONFIG_ZONE_DMA32 and CONFIG_ZONE_DMA (via
CONFIG_GENERIC_ISA_DMA).

Not that this is incomplete. What really needs to occur is that
devices using ISA DMA need to depend on ZONE_DMA.

I am also not sure if this works for all configuration. Works fine
on my desktop x86_64 system with a single zone.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.17-mm6/arch/x86_64/mm/init.c
===================================================================
--- linux-2.6.17-mm6.orig/arch/x86_64/mm/init.c 2006-07-07 01:13:06.000000000 -0700
+++ linux-2.6.17-mm6/arch/x86_64/mm/init.c 2006-07-07 01:13:14.000000000 -0700
@@ -413,15 +413,18 @@

for (i = 0; i < MAX_NR_ZONES; i++)
z[i] = 0;
-
+#ifdef CONFIG_ZONE_DMA
if (start_pfn < MAX_DMA_PFN)
z[ZONE_DMA] = MAX_DMA_PFN - start_pfn;
+#endif
+#ifdef CONFIG_ZONE_DMA32
if (start_pfn < MAX_DMA32_PFN) {
unsigned long dma32_pfn = MAX_DMA32_PFN;
if (dma32_pfn > end_pfn)
dma32_pfn = end_pfn;
z[ZONE_DMA32] = dma32_pfn - start_pfn;
}
+#endif
z[ZONE_NORMAL] = end_pfn - start_pfn;

/* Remove lower zones from higher ones. */
@@ -444,14 +447,14 @@
for (i = 0; i < MAX_NR_ZONES; i++)
h[i] += (z[i] * sizeof(struct page)) / PAGE_SIZE;

- /* The 16MB DMA zone has the kernel and other misc mappings.
+ /* The first zone has the kernel and other misc mappings.
Account them too */
- if (h[ZONE_DMA]) {
- h[ZONE_DMA] += dma_reserve;
- if (h[ZONE_DMA] >= z[ZONE_DMA]) {
+ if (h[0]) {
+ h[0] += dma_reserve;
+ if (h[0] >= z[0]) {
printk(KERN_WARNING
- "Kernel too large and filling up ZONE_DMA?\n");
- h[ZONE_DMA] = z[ZONE_DMA];
+ "Kernel too large and filling up first zone?\n");
+ h[0] = z[0];
}
}
}
Index: linux-2.6.17-mm6/arch/x86_64/Kconfig
===================================================================
--- linux-2.6.17-mm6.orig/arch/x86_64/Kconfig 2006-07-07 01:13:08.000000000 -0700
+++ linux-2.6.17-mm6/arch/x86_64/Kconfig 2006-07-07 01:13:14.000000000 -0700
@@ -24,10 +24,6 @@
bool
default y

-config ZONE_DMA32
- bool
- default y
-
config LOCKDEP_SUPPORT
bool
default y
@@ -73,10 +69,6 @@
bool
default y

-config GENERIC_ISA_DMA
- bool
- default y
-
config GENERIC_IOMAP
bool
default y
@@ -247,6 +239,23 @@

See <file:Documentation/mtrr.txt> for more information.

+config ZONE_DMA32
+ bool "32 Bit DMA Zone (only needed if memory >4GB)"
+ default y
+ help
+ Some x64 configurations have 32 bit DMA controllers that cannot
+ write to all of memory. If you have one of these and you have RAM
+ beyond the 4GB boundary then enable this option.
+
+config GENERIC_ISA_DMA
+ bool "ISA DMA zone (to support ISA legacy DMA)"
+ default y
+ help
+ If DMA for ISA boards needs to be supported then this option
+ needs to be enabled. An additional DMA zone for <16MB memory
+ will be created and memory below 16MB will be used for those
+ devices.
+
config SMP
bool "Symmetric multi-processing support"
---help---
Index: linux-2.6.17-mm6/arch/x86_64/kernel/Makefile
===================================================================
--- linux-2.6.17-mm6.orig/arch/x86_64/kernel/Makefile 2006-07-07 01:13:22.000000000 -0700
+++ linux-2.6.17-mm6/arch/x86_64/kernel/Makefile 2006-07-07 01:13:47.000000000 -0700
@@ -7,9 +7,10 @@
obj-y := process.o signal.o entry.o traps.o irq.o \
ptrace.o time.o ioport.o ldt.o setup.o i8259.o sys_x86_64.o \
x8664_ksyms.o i387.o syscall.o vsyscall.o \
- setup64.o bootflag.o e820.o reboot.o quirks.o i8237.o \
+ setup64.o bootflag.o e820.o reboot.o quirks.o \
pci-dma.o pci-nommu.o alternative.o

+obj-$(CONFIG_GENERIC_ISA_DMA) += i8237.o
obj-$(CONFIG_STACKTRACE) += stacktrace.o
obj-$(CONFIG_X86_MCE) += mce.o
obj-$(CONFIG_X86_MCE_INTEL) += mce_intel.o