[coreboot-gerrit] [S] Change in coreboot[main]: arch/x86: Configure EBDA through Kconfig

[Shuo Liu (Code Review)]

Attention is currently required from: Chen, Gang C, Jérémy Compostella.

Hello Chen, Gang C,

I'd like you to do a code review.
Please visit

https://review.coreboot.org/c/coreboot/+/84321?usp=email

to review the following change.

Change subject: arch/x86: Configure EBDA through Kconfig
......................................................................

arch/x86: Configure EBDA through Kconfig

EBDA (Extended BIOS Data Area) is a memory area below 0xA0000 and
one of the default areas where OS will scan ACPI RSDP pointer from.

coreboot's default EBDA's starting address is 0xF6000, which is in
PAM (Programmable Attribute Map) F-segment's scope. For some platforms
without writeable PAM-F segment (e.g. some simics virtual platforms),
corboot's default EBDA is not writable.

Make DEFAULT_EBDA_LOWMEM, DEFAULT_EBDA_SEGMENT, DEFAULT_EBDA_SIZE
as Kconfig items so that coreboot's EBDA could be relocated to a
writable low memory place.

Change-Id: Icd7ba0c902560f7d498934392685dc2af9c5ce09
Signed-off-by: Gang Chen 
Co-authored-by: Shuo Liu 
---
M src/arch/x86/Kconfig
M src/arch/x86/ebda.c
2 files changed, 21 insertions(+), 9 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/21/84321/1

diff --git a/src/arch/x86/Kconfig b/src/arch/x86/Kconfig
index 16d8a70..cc68f5c 100644
--- a/src/arch/x86/Kconfig
+++ b/src/arch/x86/Kconfig
@@ -422,4 +422,21 @@

The default value is 1024 bytes (1 KiB) for ChromeOS and 0 for other platforms.

+config DEFAULT_EBDA_LOWMEM
+	hex "Default EBDA low mem"
+	default 0x100000
+	help
+	  The default value of EBDA low memory is (1024 << 10).
+
+config DEFAULT_EBDA_SEGMENT
+	hex "Default EBDA segment"
+	default 0xF600
+	help
+	  The default value of EBDA segment is 0xF600.
+
+config DEFAULT_EBDA_SIZE
+	hex "Default EBDA size"
+	default 0x400
+	help
+	  The default value of EBDA size is 0x400.
 endif
diff --git a/src/arch/x86/ebda.c b/src/arch/x86/ebda.c
index e835fce..f3e8fd2 100644
--- a/src/arch/x86/ebda.c
+++ b/src/arch/x86/ebda.c
@@ -10,14 +10,9 @@
 #define X86_EBDA_SEGMENT	((void *)0x40e)
 #define X86_EBDA_LOWMEM		((void *)0x413)

-#define DEFAULT_EBDA_LOWMEM	(1024 << 10)
-#define DEFAULT_EBDA_SEGMENT	0xF600
-#define DEFAULT_EBDA_SIZE	0x400
-
-
 static void *get_ebda_start(void)
 {
-	return (void *)((uintptr_t)DEFAULT_EBDA_SEGMENT << 4);
+	return (void *)((uintptr_t)CONFIG_DEFAULT_EBDA_SEGMENT << 4);
 }

/*
@@ -55,9 +50,9 @@
    if (acpi_is_wakeup_s3())
    	return;

-	setup_ebda(DEFAULT_EBDA_LOWMEM,
-		   DEFAULT_EBDA_SEGMENT,
-		   DEFAULT_EBDA_SIZE);
+	setup_ebda(CONFIG_DEFAULT_EBDA_LOWMEM,
+		   CONFIG_DEFAULT_EBDA_SEGMENT,
+		   CONFIG_DEFAULT_EBDA_SIZE);
 }

/* Ensure EBDA is prepared before Option ROMs. */