diff options
| author | Liran Alon <liran.alon@oracle.com> | 2019-04-15 18:45:26 +0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2019-04-30 21:32:14 +0200 |
| commit | 6c6a2ab962af8f197984c45d585814f9839e86d5 (patch) | |
| tree | 7ba181b88e0f162c325694b6086154603d5bc3ab /arch/x86/kvm/vmx | |
| parent | c715eb9fe9027ed118630adb0d59acf36b848d4f (diff) | |
KVM: VMX: Nop emulation of MSR_IA32_POWER_CTL
Since commits 668fffa3f838 ("kvm: better MWAIT emulation for guestsâ€)
and 4d5422cea3b6 ("KVM: X86: Provide a capability to disable MWAIT interceptsâ€),
KVM was modified to allow an admin to configure certain guests to execute
MONITOR/MWAIT inside guest without being intercepted by host.
This is useful in case admin wishes to allocate a dedicated logical
processor for each vCPU thread. Thus, making it safe for guest to
completely control the power-state of the logical processor.
The ability to use this new KVM capability was introduced to QEMU by
commits 6f131f13e68d ("kvm: support -overcommit cpu-pm=on|offâ€) and
2266d4431132 ("i386/cpu: make -cpu host support monitor/mwaitâ€).
However, exposing MONITOR/MWAIT to a Linux guest may cause it's intel_idle
kernel module to execute c1e_promotion_disable() which will attempt to
RDMSR/WRMSR from/to MSR_IA32_POWER_CTL to manipulate the "C1E Enable"
bit. This behaviour was introduced by commit
32e9518005c8 ("intel_idle: export both C1 and C1Eâ€).
Becuase KVM doesn't emulate this MSR, running KVM with ignore_msrs=0
will cause the above guest behaviour to raise a #GP which will cause
guest to kernel panic.
Therefore, add support for nop emulation of MSR_IA32_POWER_CTL to
avoid #GP in guest in this scenario.
Future commits can optimise emulation further by reflecting guest
MSR changes to host MSR to provide guest with the ability to
fine-tune the dedicated logical processor power-state.
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/vmx')
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 6 | ||||
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.h | 2 |
2 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index c40fb667002c..3fe2020e3bc4 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1692,6 +1692,9 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) case MSR_IA32_SYSENTER_ESP: msr_info->data = vmcs_readl(GUEST_SYSENTER_ESP); break; + case MSR_IA32_POWER_CTL: + msr_info->data = vmx->msr_ia32_power_ctl; + break; case MSR_IA32_BNDCFGS: if (!kvm_mpx_supported() || (!msr_info->host_initiated && @@ -1822,6 +1825,9 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) case MSR_IA32_SYSENTER_ESP: vmcs_writel(GUEST_SYSENTER_ESP, data); break; + case MSR_IA32_POWER_CTL: + vmx->msr_ia32_power_ctl = data; + break; case MSR_IA32_BNDCFGS: if (!kvm_mpx_supported() || (!msr_info->host_initiated && diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index f879529906b4..1e42f983e0f1 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -257,6 +257,8 @@ struct vcpu_vmx { unsigned long host_debugctlmsr; + u64 msr_ia32_power_ctl; + /* * Only bits masked by msr_ia32_feature_control_valid_bits can be set in * msr_ia32_feature_control. FEATURE_CONTROL_LOCKED is always included |