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>

diff --git a/xen/arch/x86/cpu/mtrr/generic.c b/xen/arch/x86/cpu/mtrr/generic.c
index cd3c740da61a3145e1e2ebbcefa59bf68afa8ded..0f6c6b1b0c77b2b5b197b89517063bc1c7b2ef49 100644 (file)
--- a/xen/arch/x86/cpu/mtrr/generic.c
+++ b/xen/arch/x86/cpu/mtrr/generic.c
@@ -115,20 +115,6 @@ void mtrr_wrmsr(unsigned int msr, uint64_t msr_content)
        mtrr_state.overlapped = is_var_mtrr_overlapped(&mtrr_state);
 }
 
-/**
- * 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)
-{
-       uint64_t msr_content;
-
-       rdmsrl(MSR_K8_SYSCFG, msr_content);
-       mtrr_wrmsr(MSR_K8_SYSCFG, msr_content 
-                               | K8_MTRRFIXRANGE_DRAM_ENABLE
-                               | K8_MTRRFIXRANGE_DRAM_MODIFY);
-}
-
 /**
  * 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.
@@ -145,10 +131,6 @@ static void set_fixed_range(int msr, int * changed, unsigned int * msrwords)
        val = ((uint64_t)msrwords[1] << 32) | msrwords[0];
 
        if (msr_content != val) {
-               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, val);
                *changed = TRUE;
        }