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Shut up unhandled MSR warnings

PATCH Borislav Petkov 2 participants 5 messages Nov 12, 2015

Subsystems (3)
x86 KVM KVM x86
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Borislav Petkov

author maintainer
#0 lore raw

Hey Paolo,

do we apply stuff like that below?

When booting guests all the time here, dmesg gets filled up with those "unhandled rdmsr" useless warnings. The patch below shuts them up.

The only problem is that the IC CFG MSR has those fields defined starting from F15h and I don't see a way to check the family/model/stepping of the guest CPU in kvm. Is there?

Thanks.

---

arch/x86/include/asm/msr-index.h +1 -0
index b8c14bb7fc8f..08b880818fb9 100644
@@ -315,6 +315,7 @@
 #define MSR_F15H_PERF_CTR		0xc0010201
 #define MSR_F15H_NB_PERF_CTL		0xc0010240
 #define MSR_F15H_NB_PERF_CTR		0xc0010241
+#define MSR_F15H_IC_CFG			0xc0011021
 
 /* Fam 10h MSRs */
 #define MSR_FAM10H_MMIO_CONF_BASE	0xc0010058
arch/x86/kernel/cpu/amd.c +2 -2
index 4a70fc6d400a..1d76dcdf7e55 100644
@@ -665,9 +665,9 @@ static void init_amd_bd(struct cpuinfo_x86 *c)
 	 * Disable it on the affected CPUs.
 	 */
 	if ((c->x86_model >= 0x02) && (c->x86_model < 0x20)) {
-		if (!rdmsrl_safe(0xc0011021, &value) && !(value & 0x1E)) {
+		if (!rdmsrl_safe(MSR_F15H_IC_CFG, &value) && !(value & 0x1E)) {
 			value |= 0x1E;
-			wrmsrl_safe(0xc0011021, value);
+			wrmsrl_safe(MSR_F15H_IC_CFG, value);
 		}
 	}
 }
arch/x86/kvm/svm.c +3 -0
index 2f9ed1ff0632..7948cdeacbfe 100644
@@ -3141,6 +3141,9 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_IA32_UCODE_REV:
 		msr_info->data = 0x01000065;
 		break;
+	case MSR_F15H_IC_CFG:
+		msr_info->data = 0x1E;
+		break;
 	default:
 		return kvm_get_msr_common(vcpu, msr_info);
 	}
Signature · 4 lines
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
maintainer
#1 lore raw
Quoted 3 lines · Borislav Petkov

Hey Paolo,

do we apply stuff like that below?

If we really need to, we do.

Quoted 6 lines

When booting guests all the time here, dmesg gets filled up with those "unhandled rdmsr" useless warnings. The patch below shuts them up.

The only problem is that the IC CFG MSR has those fields defined starting from F15h and I don't see a way to check the family/model/stepping of the guest CPU in kvm. Is there?

Yes, see guest_cpuid_has_* for an example of reading the CPUID values.

But if it's defined for _all_ models starting at family 21, we can just do it unconditionally.

Paolo

author maintainer
#2 lore raw
Quoted 4 lines · Paolo Bonzini

Yes, see guest_cpuid_has_* for an example of reading the CPUID values.

But if it's defined for _all_ models starting at family 21, we can just do it unconditionally.

The thing is, those bits are Reserved again on the next family 22. Lemme take a look at guest_cpuid_has_* and see how ugly it gets.

Thanks.

Signature · 4 lines
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
author maintainer
#3 lore raw
Quoted 8 lines · Borislav Petkov
Quoted 4 lines · Paolo Bonzini

Yes, see guest_cpuid_has_* for an example of reading the CPUID values.

But if it's defined for _all_ models starting at family 21, we can just do it unconditionally.

The thing is, those bits are Reserved again on the next family 22. Lemme take a look at guest_cpuid_has_* and see how ugly it gets.

Ok, I see there's guest_cpuid_is_amd() but I'd need also family and model.

How about adding also

guest_cpuid_family(), guest_cpuid_model(), guest_cpuid_stepping()? Those could be quite useful in other contexts maybe.

Or, I can do a single function which simply returns CPUID_1_EAX of the guest vcpu and caller can then pick stuff apart...

Thoughts?

Signature · 4 lines
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
maintainer
#4 lore raw
Quoted 8 lines · Borislav Petkov
Quoted 7 lines
Quoted 7 lines
Quoted 4 lines
Quoted 4 lines

Yes, see guest_cpuid_has_* for an example of reading the CPUID values.

But if it's defined for _all_ models starting at family 21, we can just do it unconditionally.

The thing is, those bits are Reserved again on the next family 22. Lemme take a look at guest_cpuid_has_* and see how ugly it gets.

Quoted 6 lines

Ok, I see there's guest_cpuid_is_amd() but I'd need also family and model.

How about adding also

guest_cpuid_family(), guest_cpuid_model(), guest_cpuid_stepping()? Those could be quite useful in other contexts maybe.

Sure, that's what I meant by "for an example". :)

Paolo