From ed85c0685321a139cefd6622b21467643f0159e1 Mon Sep 17 00:00:00 2001 From: Andre Przywara Date: Thu, 25 Jun 2009 12:36:49 +0200 Subject: KVM: introduce module parameter for ignoring unknown MSRs accesses KVM will inject a #GP into the guest if that tries to access unhandled MSRs. This will crash many guests. Although it would be the correct way to actually handle these MSRs, we introduce a runtime switchable module param called "ignore_msrs" (defaults to 0). If this is Y, unknown MSR reads will return 0, while MSR writes are simply dropped. In both cases we print a message to dmesg to inform the user about that. You can change the behaviour at any time by saying: # echo 1 > /sys/modules/kvm/parameters/ignore_msrs Signed-off-by: Andre Przywara Signed-off-by: Avi Kivity --- arch/x86/kvm/x86.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 6aace61fdb62..0be75d53b7fd 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -83,6 +83,9 @@ struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu, struct kvm_x86_ops *kvm_x86_ops; EXPORT_SYMBOL_GPL(kvm_x86_ops); +int ignore_msrs = 0; +module_param_named(ignore_msrs, ignore_msrs, bool, S_IRUGO | S_IWUSR); + struct kvm_stats_debugfs_item debugfs_entries[] = { { "pf_fixed", VCPU_STAT(pf_fixed) }, { "pf_guest", VCPU_STAT(pf_guest) }, @@ -930,8 +933,15 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data) "0x%x data 0x%llx\n", msr, data); break; default: - pr_unimpl(vcpu, "unhandled wrmsr: 0x%x data %llx\n", msr, data); - return 1; + if (!ignore_msrs) { + pr_unimpl(vcpu, "unhandled wrmsr: 0x%x data %llx\n", + msr, data); + return 1; + } else { + pr_unimpl(vcpu, "ignored wrmsr: 0x%x data %llx\n", + msr, data); + break; + } } return 0; } @@ -1078,8 +1088,14 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata) case MSR_IA32_MC0_CTL ... MSR_IA32_MC0_CTL + 4 * KVM_MAX_MCE_BANKS - 1: return get_msr_mce(vcpu, msr, pdata); default: - pr_unimpl(vcpu, "unhandled rdmsr: 0x%x\n", msr); - return 1; + if (!ignore_msrs) { + pr_unimpl(vcpu, "unhandled rdmsr: 0x%x\n", msr); + return 1; + } else { + pr_unimpl(vcpu, "ignored rdmsr: 0x%x\n", msr); + data = 0; + } + break; } *pdata = data; return 0; -- cgit v1.2.2