File 23154-x86-amd-iorr-no-rdwr.patch of Package xen.import4929

# HG changeset patch
# User Wei Huang <wei.huang2@amd.com>
# Date 1302076933 -3600
# Node ID 42fa70e0761bbb0596618ca5323664f31a2faa76
# Parent  8fb61c9ebe499b576687907d164da07802414925
x86, amd, MTRR: remove k8_enable_fixed_iorrs()

AMD64 defines two special bits (bit 3 and 4) RdMem and WrMem in fixed
MTRR type. Their values are supposed to be 0 after BIOS hands the
control to OS according to AMD BKDG. Unless OS specificially turn them
on, they are kept 0 all the time. As a result, k8_enable_fixed_iorrs()
is unnecessary and removed from upstream kernel (see
https://patchwork.kernel.org/patch/11425/). This patch does the same
thing.

Signed-off-by: Wei Huang <wei.huang2@amd.com>

--- a/xen/arch/x86/cpu/mtrr/generic.c
+++ b/xen/arch/x86/cpu/mtrr/generic.c
@@ -116,20 +116,6 @@ void mtrr_wrmsr(unsigned msr, unsigned a
 }
 
 /**
- * Enable and allow read/write of extended fixed-range MTRR bits on K8 CPUs
- * see AMD publication no. 24593, chapter 3.2.1 for more information
- */
-static inline void k8_enable_fixed_iorrs(void)
-{
-	unsigned lo, hi;
-
-	rdmsr(MSR_K8_SYSCFG, lo, hi);
-	mtrr_wrmsr(MSR_K8_SYSCFG, lo
-				| K8_MTRRFIXRANGE_DRAM_ENABLE
-				| K8_MTRRFIXRANGE_DRAM_MODIFY, hi);
-}
-
-/**
  * Checks and updates an fixed-range MTRR if it differs from the value it
  * should have. If K8 extenstions are wanted, update the K8 SYSCFG MSR also.
  * see AMD publication no. 24593, chapter 7.8.1, page 233 for more information
@@ -144,10 +130,6 @@ static void set_fixed_range(int msr, int
 	rdmsr(msr, lo, hi);
 
 	if (lo != msrwords[0] || hi != msrwords[1]) {
-		if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
-		    boot_cpu_data.x86 == 15 &&
-		    ((msrwords[0] | msrwords[1]) & K8_MTRR_RDMEM_WRMEM_MASK))
-			k8_enable_fixed_iorrs();
 		mtrr_wrmsr(msr, msrwords[0], msrwords[1]);
 		*changed = TRUE;
 	}