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author | Wei Huang <wei.huang2@amd.com> | 2011-04-07 15:44:19 +0100 |
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committer | Wei Huang <wei.huang2@amd.com> | 2011-04-07 15:44:19 +0100 |
commit | 5cd35299674dece1d5b99c745b2ddd54a9b7895d (patch) | |
tree | 1f804b897dd7a32b4acba93520761bc5e7ba1a2e | |
parent | 64ddf302cfb53c679eb1dbe23a5028b1a7725d43 (diff) | |
download | xen-5cd35299674dece1d5b99c745b2ddd54a9b7895d.tar.gz xen-5cd35299674dece1d5b99c745b2ddd54a9b7895d.tar.bz2 xen-5cd35299674dece1d5b99c745b2ddd54a9b7895d.zip |
x86, amd, MTRR: correct DramModEn bit of SYS_CFG MSR
Some buggy BIOS might set SYS_CFG DramModEn bit to 1, which can cause
unexpected behavior on AMD platforms. This patch clears DramModEn bit
if it is 1.
Signed-off-by: Wei Huang <wei.huang2@amd.com>
xen-unstable changeset: 23153:8fb61c9ebe49
xen-unstable date: Wed Apr 06 09:01:31 2011 +0100
-rw-r--r-- | xen/arch/x86/cpu/amd.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/xen/arch/x86/cpu/amd.c b/xen/arch/x86/cpu/amd.c index d236b30d92..d0c0b1602f 100644 --- a/xen/arch/x86/cpu/amd.c +++ b/xen/arch/x86/cpu/amd.c @@ -347,6 +347,32 @@ static void check_disable_c1e(unsigned int port, u8 value) on_each_cpu(disable_c1e, NULL, 1); } +/* + * BIOS is expected to clear MtrrFixDramModEn bit. According to AMD BKDG : + * "The MtrrFixDramModEn bit should be set to 1 during BIOS initalization of + * the fixed MTRRs, then cleared to 0 for operation." + */ +static void check_syscfg_dram_mod_en(void) +{ + uint64_t syscfg; + static bool_t printed = 0; + + if (!((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) && + (boot_cpu_data.x86 >= 0x0f))) + return; + + rdmsrl(MSR_K8_SYSCFG, syscfg); + if (!(syscfg & K8_MTRRFIXRANGE_DRAM_MODIFY)) + return; + + if (!test_and_set_bool(printed)) + printk(KERN_ERR "MTRR: SYSCFG[MtrrFixDramModEn] not " + "cleared by BIOS, clearing this bit\n"); + + syscfg &= ~K8_MTRRFIXRANGE_DRAM_MODIFY; + wrmsrl(MSR_K8_SYSCFG, syscfg); +} + static void __devinit init_amd(struct cpuinfo_x86 *c) { u32 l, h; @@ -624,6 +650,8 @@ static void __devinit init_amd(struct cpuinfo_x86 *c) set_cpuidmask(c); + check_syscfg_dram_mod_en(); + start_svm(c); } |