From eda689ee9aa29e6c4e791a7f295bc4a0a3ad5d83 Mon Sep 17 00:00:00 2001
From: Joshua Wise <joshua@nyus.joshuawise.com>
Date: Sat, 6 Dec 2008 08:56:14 -0500
Subject: [PATCH] Enable caching while in SMM.

---
 aseg-paging/smi.c |  7 +++++++
 include/msr.h     | 18 ++++++++++++++++++
 2 files changed, 25 insertions(+)
 create mode 100644 include/msr.h

diff --git a/aseg-paging/smi.c b/aseg-paging/smi.c
index 7f75a85..d519341 100644
--- a/aseg-paging/smi.c
+++ b/aseg-paging/smi.c
@@ -7,6 +7,7 @@
 #include <serial.h>
 #include <fb.h>
 #include <output.h>
+#include <msr.h>
 #include "../net/net.h"
 #include "vga-overlay.h"
 
@@ -18,6 +19,9 @@ void smi_entry(void)
 {
 	char statstr[512];
 
+	/* Reenable caching on SMRAM. */
+	WRMSR(0x202, (RDMSR(0x202) & ~(0xFFULL)) | 0x06ULL);
+
 	pcisave = inl(0xCF8);
 	vgasave = inb(0x3D4);
 	pci_unbother_all();
@@ -51,6 +55,9 @@ void smi_entry(void)
 	pci_bother_all();
 	outl(0xCF8, pcisave);
 	outb(0x3D4, vgasave);
+	
+	/* Disable caching on SMRAM again, to prevent the user from whacking us. */
+	WRMSR(0x202, RDMSR(0x202) & ~(0xFFULL));
 }
 
 extern void timer_handler(smi_event_t ev);
diff --git a/include/msr.h b/include/msr.h
new file mode 100644
index 0000000..0bed091
--- /dev/null
+++ b/include/msr.h
@@ -0,0 +1,18 @@
+#ifndef _MSR_H
+#define _MSR_H
+
+#define WRMSR(ad, da) \
+	do { \
+		unsigned long __a = (ad); \
+		unsigned long long __d = (da); \
+		asm volatile("wrmsr" : : "c" (__a), "A" (__d)); \
+	} while (0)
+#define RDMSR(ad) \
+	({ \
+		unsigned long __a = (ad); \
+		unsigned long long __d; \
+		asm volatile("rdmsr" : "=A" (__d) : "c" (__a)); \
+		__d; \
+	})
+
+#endif
-- 
2.43.0