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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