[Xen-devel] [PATCH] arch/x86: convert bigmem to Kconfig

[Doug Goldstein <cardoe@xxxxxxxxxx>]

Convert the bigmem build option to Kconfig.

Signed-off-by: Doug Goldstein <cardoe@xxxxxxxxxx>
---
The test:

$ grep CONFIG_BIGMEM .config
# CONFIG_BIGMEM is not set
$ pahole xen-syms -C page_info
....
        /* size: 32, cachelines: 1, members: 5 */

<rebuild Xen>

$ grep CONFIG_BIGMEM .config
CONFIG_BIGMEM=y
$ pahole xen-syms -C page_info
....
        /* size: 48, cachelines: 1, members: 5 */
---
 xen/arch/x86/Kconfig  | 12 ++++++++++++
 xen/arch/x86/Rules.mk |  2 --
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index 7d2ed96..90b4216 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -25,6 +25,18 @@ config ARCH_DEFCONFIG
 
 menu "Architecture Features"
 
+config BIGMEM
+       bool "big memory support"
+       default n
+       ---help---
+         Allows Xen to support up to 123Tb of memory.
+
+         This requires growing struct page_info from 32 to 48 bytes as well
+         as shrinking the always accessible direct mapped memory range from
+         5Tb to 3.5Tb.
+
+         If unsure, say N.
+
 endmenu
 
 source "common/Kconfig"
diff --git a/xen/arch/x86/Rules.mk b/xen/arch/x86/Rules.mk
index b76a754..a108d24 100644
--- a/xen/arch/x86/Rules.mk
+++ b/xen/arch/x86/Rules.mk
@@ -23,7 +23,6 @@ $(call as-insn-check,CFLAGS,CC,".equ \"x\"$$(comma)1", \
                      '-D__OBJECT_LABEL__=$(subst $(BASEDIR)/,,$(CURDIR))/$$@')
 
 shadow-paging ?= y
-bigmem        ?= n
 
 CFLAGS += -mno-red-zone -mno-sse -fpic
 CFLAGS += -fno-asynchronous-unwind-tables
@@ -33,4 +32,3 @@ CFLAGS += -DGCC_HAS_VISIBILITY_ATTRIBUTE
 endif
 
 CFLAGS-$(shadow-paging) += -DCONFIG_SHADOW_PAGING
-CFLAGS-$(bigmem)        += -DCONFIG_BIGMEM
-- 
2.4.10


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