cpu/x86: Add 1GiB pages for memory access up to 512GiB
Current pagetable implementation allows memory access up to 4GiB using
2MiB pages. If user wants to access more than 4GiB with a 2MiB page it
will require more pagetable entries. By using a 1GiB page table, users
can access more than 4GiB of memory while reducing the number of
pagetable entries. This patch enables memory access up to 512GiB through
1GiB pages by selecting USE_1G_PAGES_TLB in Kconfig.
TEST: Verified in 64bit mode boot and access above 4GiB
Change-Id: Id569ae5b50abf5b72e4db33b5e4cd802399e76ec
Signed-off-by: Ashish Kumar Mishra <ashish.k.mishra@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80088
Reviewed-by: Wonkyu Kim <wonkyu.kim@intel.com>
Reviewed-by: Jérémy Compostella <jeremy.compostella@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
diff --git a/src/cpu/x86/64bit/Makefile.mk b/src/cpu/x86/64bit/Makefile.mk
index 24a5a96..680ab2d 100644
--- a/src/cpu/x86/64bit/Makefile.mk
+++ b/src/cpu/x86/64bit/Makefile.mk
@@ -3,8 +3,14 @@
all_x86-y += mode_switch.S
all_x86-y += mode_switch2.S
+ifeq ($(CONFIG_USE_1G_PAGETABLES),y)
+PAGETABLE_SRC := pt1G.S
+else
+PAGETABLE_SRC := pt.S
+endif
+
# Add --defsym=_start=0 to suppress a linker warning.
-$(objcbfs)/pt: $(dir)/pt.S $(obj)/config.h
+$(objcbfs)/pt: $(dir)/$(PAGETABLE_SRC) $(obj)/config.h
$(CC_bootblock) $(CFLAGS_bootblock) $(CPPFLAGS_bootblock) -o $@.tmp $< -Wl,--section-start=.rodata=$(CONFIG_ARCH_X86_64_PGTBL_LOC),--defsym=_start=0
$(OBJCOPY_ramstage) -Obinary -j .rodata $@.tmp $@
rm $@.tmp
diff --git a/src/cpu/x86/64bit/pt1G.S b/src/cpu/x86/64bit/pt1G.S
new file mode 100644
index 0000000..3ddb620
--- /dev/null
+++ b/src/cpu/x86/64bit/pt1G.S
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+/*
+ * For reference see "AMD64 Architecture Programmer's Manual Volume 2",
+ * Document 24593-Rev. 3.31-July 2019 Chapter 5.3.4
+ *
+ * Page table attributes: WB, User+Supervisor, Present, Writeable, Accessed, Dirty
+ */
+
+.section .rodata
+#define _PRES (1ULL << 0)
+#define _RW (1ULL << 1)
+#define _US (1ULL << 2)
+#define _A (1ULL << 5)
+#define _D (1ULL << 6)
+#define _PS (1ULL << 7)
+#define _GEN_DIR(a) (_PRES + _RW + _US + _A + (a))
+#define _GEN_PAGE(a) (_PRES + _RW + _US + _PS + _A + _D + (a))
+
+.global PM4LE
+.align 4096
+PM4LE:
+.quad _GEN_DIR(PDE_table)
+
+.align 4096
+PDE_table: /* identity map 1GiB pages * 512 */
+.rept 512
+.quad _GEN_PAGE(0x40000000 * ((. - PDE_table) >> 3))
+.endr
diff --git a/src/cpu/x86/Kconfig b/src/cpu/x86/Kconfig
index 4e17690..6c784b4 100644
--- a/src/cpu/x86/Kconfig
+++ b/src/cpu/x86/Kconfig
@@ -150,6 +150,13 @@
bool
default n
+config USE_1G_PAGES_TLB
+ bool
+ default n
+ help
+ Select this option to enable access to up to 512 GiB of memory
+ by using 1 GiB large pages.
+
config SMM_ASEG
bool
default n