[PATCH 7/9] x86, RAS: Add function enabling direct writes to MCE MSRs

[Borislav Petkov <bp@amd64.org>]

From: Borislav Petkov <borislav.petkov@amd.com>

Normally, writing to MCE MSRs causes a #GP. Add a function to enable
direct accesses to those MSRs.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
---
 arch/x86/kernel/cpu/ras/amd/mce-inject.c |   24 ++++++++++++++++++++++++
 1 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/cpu/ras/amd/mce-inject.c b/arch/x86/kernel/cpu/ras/amd/mce-inject.c
index fdec361..1b797bd 100644
--- a/arch/x86/kernel/cpu/ras/amd/mce-inject.c
+++ b/arch/x86/kernel/cpu/ras/amd/mce-inject.c
@@ -53,6 +53,30 @@ DEFINE_SIMPLE_ATTRIBUTE(misc_fops, inj_misc_get, inj_misc_set, "%llx\n");
 DEFINE_SIMPLE_ATTRIBUTE(addr_fops, inj_addr_get, inj_addr_set, "%llx\n");
 
 /*
+ * Caller needs to be make sure this cpu doesn't disappear
+ * from under us, i.e.: get_cpu/put_cpu.
+ */
+static int toggle_hw_mce_inject(unsigned int cpu, bool enable)
+{
+	u32 l, h;
+	int err;
+
+	err = rdmsr_on_cpu(cpu, MSR_K7_HWCR, &l, &h);
+	if (err) {
+		printk(KERN_ERR "%s: error reading HWCR\n", __func__);
+		return err;
+	}
+
+	enable ? (l |= BIT(18)) : (l &= ~BIT(18));
+
+	err = wrmsr_on_cpu(cpu, MSR_K7_HWCR, l, h);
+	if (err)
+		printk(KERN_ERR "%s: error writing HWCR\n", __func__);
+
+	return err;
+}
+
+/*
  * This denotes into which bank we're injecting and triggers
  * the injection, at the same time.
  */
-- 
1.7.4.rc2