From: Paolo Bonzini <pbonzini@redhat.com> To: Vitaly Kuznetsov <vkuznets@redhat.com>, kvm@vger.kernel.org Cc: Sean Christopherson <sean.j.christopherson@intel.com>, Jim Mattson <jmattson@google.com>, linux-kernel@vger.kernel.org, Liran Alon <liran.alon@oracle.com>, Roman Kagan <rkagan@virtuozzo.com> Subject: Re: [PATCH RFC 2/3] x86/kvm/hyper-v: move VMX controls sanitization out of nested_enable_evmcs() Date: Sun, 19 Jan 2020 09:54:44 +0100 Message-ID: <6c4bdb57-08fb-2c2d-9234-b7efffeb72ed@redhat.com> (raw) In-Reply-To: <20200115171014.56405-3-vkuznets@redhat.com> On 15/01/20 18:10, Vitaly Kuznetsov wrote: > With fine grained VMX feature enablement QEMU>=4.2 tries to do KVM_SET_MSRS > with default (matching CPU model) values and in case eVMCS is also enabled, > fails. > > It would be possible to drop VMX feature filtering completely and make > this a guest's responsibility: if it decides to use eVMCS it should know > which fields are available and which are not. Hyper-V mostly complies to > this, however, there is at least one problematic control: > SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES > which Hyper-V enables. As there is no 'apic_addr_field' in eVMCS, we > fail to handle this properly in KVM. It is unclear how this is supposed > to work, genuine Hyper-V doesn't expose the control so it is possible that > this is just a bug (in Hyper-V). Yes, it most likely is and it would be nice if Microsoft fixed it, but I guess we're stuck with it for existing Windows versions. Well, for one we found a bug in Hyper-V and not the converse. :) There is a problem with this approach, in that we're stuck with it forever due to live migration. But I guess if in the future eVMCS v2 adds an apic_address field we can limit the hack to eVMCS v1. Another possibility is to use the quirks mechanism but it's overkill for now. Unless there are objections, I plan to apply these patches. Paolo > Move VMX controls sanitization from nested_enable_evmcs() to vmx_get_msr(), > this allows userspace to keep setting controls it wants and at the same > time hides them from the guest. > > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> > --- > arch/x86/kvm/vmx/evmcs.c | 38 ++++++++++++++++++++++++++++++++------ > arch/x86/kvm/vmx/evmcs.h | 1 + > arch/x86/kvm/vmx/vmx.c | 10 ++++++++-- > 3 files changed, 41 insertions(+), 8 deletions(-) > > diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c > index 89c3e0caf39f..b5d6582ba589 100644 > --- a/arch/x86/kvm/vmx/evmcs.c > +++ b/arch/x86/kvm/vmx/evmcs.c > @@ -346,6 +346,38 @@ uint16_t nested_get_evmcs_version(struct kvm_vcpu *vcpu) > return 0; > } > > +void nested_evmcs_filter_control_msr(u32 msr_index, u64 *pdata) > +{ > + u32 ctl_low = (u32)*pdata, ctl_high = (u32)(*pdata >> 32); > + /* > + * Enlightened VMCS doesn't have certain fields, make sure we don't > + * expose unsupported controls to L1. > + */ > + > + switch (msr_index) { > + case MSR_IA32_VMX_PINBASED_CTLS: > + case MSR_IA32_VMX_TRUE_PINBASED_CTLS: > + ctl_high &= ~EVMCS1_UNSUPPORTED_PINCTRL; > + break; > + case MSR_IA32_VMX_EXIT_CTLS: > + case MSR_IA32_VMX_TRUE_EXIT_CTLS: > + ctl_high &= ~EVMCS1_UNSUPPORTED_VMEXIT_CTRL; > + break; > + case MSR_IA32_VMX_ENTRY_CTLS: > + case MSR_IA32_VMX_TRUE_ENTRY_CTLS: > + ctl_high &= ~EVMCS1_UNSUPPORTED_VMENTRY_CTRL; > + break; > + case MSR_IA32_VMX_PROCBASED_CTLS2: > + ctl_high &= ~EVMCS1_UNSUPPORTED_2NDEXEC; > + break; > + case MSR_IA32_VMX_VMFUNC: > + ctl_low &= ~EVMCS1_UNSUPPORTED_VMFUNC; > + break; > + } > + > + *pdata = ctl_low | ((u64)ctl_high << 32); > +} > + > int nested_enable_evmcs(struct kvm_vcpu *vcpu, > uint16_t *vmcs_version) > { > @@ -356,11 +388,5 @@ int nested_enable_evmcs(struct kvm_vcpu *vcpu, > if (vmcs_version) > *vmcs_version = nested_get_evmcs_version(vcpu); > > - vmx->nested.msrs.pinbased_ctls_high &= ~EVMCS1_UNSUPPORTED_PINCTRL; > - vmx->nested.msrs.entry_ctls_high &= ~EVMCS1_UNSUPPORTED_VMENTRY_CTRL; > - vmx->nested.msrs.exit_ctls_high &= ~EVMCS1_UNSUPPORTED_VMEXIT_CTRL; > - vmx->nested.msrs.secondary_ctls_high &= ~EVMCS1_UNSUPPORTED_2NDEXEC; > - vmx->nested.msrs.vmfunc_controls &= ~EVMCS1_UNSUPPORTED_VMFUNC; > - > return 0; > } > diff --git a/arch/x86/kvm/vmx/evmcs.h b/arch/x86/kvm/vmx/evmcs.h > index 07ebf6882a45..b88d9807a796 100644 > --- a/arch/x86/kvm/vmx/evmcs.h > +++ b/arch/x86/kvm/vmx/evmcs.h > @@ -201,5 +201,6 @@ bool nested_enlightened_vmentry(struct kvm_vcpu *vcpu, u64 *evmcs_gpa); > uint16_t nested_get_evmcs_version(struct kvm_vcpu *vcpu); > int nested_enable_evmcs(struct kvm_vcpu *vcpu, > uint16_t *vmcs_version); > +void nested_evmcs_filter_control_msr(u32 msr_index, u64 *pdata); > > #endif /* __KVM_X86_VMX_EVMCS_H */ > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index e3394c839dea..8eb74618b8d8 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -1849,8 +1849,14 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) > case MSR_IA32_VMX_BASIC ... MSR_IA32_VMX_VMFUNC: > if (!nested_vmx_allowed(vcpu)) > return 1; > - return vmx_get_vmx_msr(&vmx->nested.msrs, msr_info->index, > - &msr_info->data); > + if (vmx_get_vmx_msr(&vmx->nested.msrs, msr_info->index, > + &msr_info->data)) > + return 1; > + if (!msr_info->host_initiated && > + vmx->nested.enlightened_vmcs_enabled) > + nested_evmcs_filter_control_msr(msr_info->index, > + &msr_info->data); > + break; > case MSR_IA32_RTIT_CTL: > if (pt_mode != PT_MODE_HOST_GUEST) > return 1; >
next prev parent reply index Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-01-15 17:10 [PATCH RFC 0/3] x86/kvm/hyper-v: fix enlightened VMCS & QEMU4.2 Vitaly Kuznetsov 2020-01-15 17:10 ` [PATCH RFC 1/3] x86/kvm/hyper-v: remove stale evmcs_already_enabled check from nested_enable_evmcs() Vitaly Kuznetsov 2020-01-15 22:50 ` Liran Alon 2020-01-15 17:10 ` [PATCH RFC 2/3] x86/kvm/hyper-v: move VMX controls sanitization out of nested_enable_evmcs() Vitaly Kuznetsov 2020-01-15 22:49 ` Liran Alon 2020-01-16 8:37 ` Vitaly Kuznetsov 2020-02-03 15:11 ` Vitaly Kuznetsov 2020-01-15 23:27 ` Sean Christopherson 2020-01-15 23:30 ` Liran Alon 2020-01-16 8:51 ` Vitaly Kuznetsov 2020-01-16 16:19 ` Sean Christopherson 2020-01-16 16:57 ` Vitaly Kuznetsov 2020-01-17 6:31 ` Sean Christopherson 2020-01-18 21:42 ` Paolo Bonzini 2020-01-19 8:54 ` Paolo Bonzini [this message] 2020-01-22 5:47 ` Sean Christopherson 2020-01-22 9:37 ` Vitaly Kuznetsov 2020-01-22 14:33 ` Paolo Bonzini 2020-01-22 15:08 ` Vitaly Kuznetsov 2020-01-22 15:51 ` Sean Christopherson 2020-01-22 16:29 ` Vitaly Kuznetsov 2020-01-22 16:40 ` Paolo Bonzini 2020-01-23 9:15 ` Vitaly Kuznetsov 2020-01-23 19:09 ` Vitaly Kuznetsov 2020-01-24 17:25 ` Sean Christopherson 2020-01-27 15:38 ` Vitaly Kuznetsov 2020-01-27 17:53 ` Paolo Bonzini 2020-01-27 21:52 ` Vitaly Kuznetsov 2020-01-27 18:17 ` Sean Christopherson 2020-01-15 17:10 ` [PATCH RFC 3/3] x86/kvm/hyper-v: don't allow to turn on unsupported VMX controls for nested guests Vitaly Kuznetsov 2020-01-15 22:59 ` Liran Alon 2020-01-16 8:55 ` Vitaly Kuznetsov 2020-01-16 16:21 ` Sean Christopherson 2020-01-19 8:57 ` Paolo Bonzini
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