Re: [PATCH v3 5/6] x86/MCE: Save MCA control bits that get set in hardware

[Borislav Petkov]

On Fri, May 17, 2019 at 10:26:49AM -0700, Luck, Tony wrote:
> Which is a quirk for some models where we don't want to do
> the "write all 1s and see what sticks"

Ok, then we have to do what you suggested yesterday. I've added a short
comment so that I don't get lost again next time.

---
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 5bcecadcf4d9..9056f0a2a90d 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -1493,6 +1493,11 @@ static int __mcheck_cpu_mce_banks_init(void)
 	for (i = 0; i < n_banks; i++) {
 		struct mce_bank *b = &mce_banks[i];
 
+		/*
+		 * Init them all, __mcheck_cpu_apply_quirks() is going to apply
+		 * the required vendor quirks before
+		 * __mcheck_cpu_init_clear_banks() does the final bank setup.
+		 */
 		b->ctl = -1ULL;
 		b->init = 1;
 	}
@@ -1562,15 +1567,21 @@ static void __mcheck_cpu_init_generic(void)
 static void __mcheck_cpu_init_clear_banks(void)
 {
 	struct mce_bank *mce_banks = this_cpu_read(mce_banks_array);
+	u64 msrval;
 	int i;
 
 	for (i = 0; i < this_cpu_read(mce_num_banks); i++) {
 		struct mce_bank *b = &mce_banks[i];
 
-		if (!b->init)
-			continue;
-		wrmsrl(msr_ops.ctl(i), b->ctl);
-		wrmsrl(msr_ops.status(i), 0);
+		if (b->init) {
+			/* Check if any bits are implemented in h/w */
+			wrmsrl(msr_ops.ctl(i), b->ctl);
+			rdmsrl(msr_ops.ctl(i), msrval);
+
+			b->init = !!msrval;
+
+			wrmsrl(msr_ops.status(i), 0);
+		}
 	}
 }
 
@@ -2095,6 +2106,9 @@ static ssize_t show_bank(struct device *s, struct device_attribute *attr,
 
 	b = &per_cpu(mce_banks_array, s->id)[bank];
 
+	if (!b->init)
+		return -ENODEV;
+
 	return sprintf(buf, "%llx\n", b->ctl);
 }
 
@@ -2113,6 +2127,9 @@ static ssize_t set_bank(struct device *s, struct device_attribute *attr,
 
 	b = &per_cpu(mce_banks_array, s->id)[bank];
 
+	if (!b->init)
+		return -ENODEV;
+
 	b->ctl = new;
 	mce_restart();
 
-- 
2.21.0

-- 
Regards/Gruss,
    Boris.

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