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Date: Fri, 1 Jul 2022 15:54:46 -0700
From: Jim Mattson <jmattson@...gle.com>
To: Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <seanjc@...gle.com>,
Anirudh Rayabharam <anrayabh@...ux.microsoft.com>,
Wanpeng Li <wanpengli@...cent.com>,
Maxim Levitsky <mlevitsk@...hat.com>,
linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 24/28] KVM: nVMX: Use sanitized allowed-1 bits for VMX
control MSRs
On Wed, Jun 29, 2022 at 8:07 AM Vitaly Kuznetsov <vkuznets@...hat.com> wrote:
>
> Using raw host MSR values for setting up nested VMX control MSRs is
> incorrect as some features need to disabled, e.g. when KVM runs as
> a nested hypervisor on Hyper-V and uses Enlightened VMCS or when a
> workaround for IA32_PERF_GLOBAL_CTRL is applied. For non-nested VMX, this
> is done in setup_vmcs_config() and the result is stored in vmcs_config.
> Use it for setting up allowed-1 bits in nested VMX MSRs too.
>
> Suggested-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> ---
> arch/x86/kvm/vmx/nested.c | 34 ++++++++++++++++------------------
> arch/x86/kvm/vmx/nested.h | 2 +-
> arch/x86/kvm/vmx/vmx.c | 5 ++---
> 3 files changed, 19 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 88625965f7b7..e5b19b5e6cab 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -6565,8 +6565,13 @@ static u64 nested_vmx_calc_vmcs_enum_msr(void)
> * bit in the high half is on if the corresponding bit in the control field
> * may be on. See also vmx_control_verify().
> */
> -void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps)
> +void nested_vmx_setup_ctls_msrs(struct vmcs_config *vmcs_conf, u32 ept_caps)
> {
> + struct nested_vmx_msrs *msrs = &vmcs_conf->nested;
> +
> + /* Take the allowed-1 bits from KVM's sanitized VMCS configuration. */
> + u32 ignore_high;
> +
Giving this object a name seems gauche.
> /*
> * Note that as a general rule, the high half of the MSRs (bits in
> * the control fields which may be 1) should be initialized by the
> @@ -6583,11 +6588,11 @@ void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps)
> */
>
> /* pin-based controls */
> - rdmsr(MSR_IA32_VMX_PINBASED_CTLS,
> - msrs->pinbased_ctls_low,
> - msrs->pinbased_ctls_high);
> + rdmsr(MSR_IA32_VMX_PINBASED_CTLS, msrs->pinbased_ctls_low, ignore_high);
Perhaps "(u32){0}" rather than "ignore_high"?
> msrs->pinbased_ctls_low |=
> PIN_BASED_ALWAYSON_WITHOUT_TRUE_MSR;
NYC, but why is this one '|=', and the rest just '='? Does there exist
a CPU that requires more than PIN_BASED_ALWAYSON_WITHOUT_TRUE_MSR?
> +
> + msrs->pinbased_ctls_high = vmcs_conf->pin_based_exec_ctrl;
> msrs->pinbased_ctls_high &=
> PIN_BASED_EXT_INTR_MASK |
> PIN_BASED_NMI_EXITING |
> @@ -6598,12 +6603,10 @@ void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps)
> PIN_BASED_VMX_PREEMPTION_TIMER;
>
> /* exit controls */
> - rdmsr(MSR_IA32_VMX_EXIT_CTLS,
> - msrs->exit_ctls_low,
> - msrs->exit_ctls_high);
> msrs->exit_ctls_low =
> VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR;
>
> + msrs->exit_ctls_high = vmcs_conf->vmexit_ctrl;
> msrs->exit_ctls_high &=
> #ifdef CONFIG_X86_64
> VM_EXIT_HOST_ADDR_SPACE_SIZE |
> @@ -6619,11 +6622,10 @@ void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps)
> msrs->exit_ctls_low &= ~VM_EXIT_SAVE_DEBUG_CONTROLS;
>
> /* entry controls */
> - rdmsr(MSR_IA32_VMX_ENTRY_CTLS,
> - msrs->entry_ctls_low,
> - msrs->entry_ctls_high);
> msrs->entry_ctls_low =
> VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR;
> +
> + msrs->entry_ctls_high = vmcs_conf->vmentry_ctrl;
> msrs->entry_ctls_high &=
> #ifdef CONFIG_X86_64
> VM_ENTRY_IA32E_MODE |
> @@ -6637,11 +6639,10 @@ void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps)
> msrs->entry_ctls_low &= ~VM_ENTRY_LOAD_DEBUG_CONTROLS;
>
> /* cpu-based controls */
> - rdmsr(MSR_IA32_VMX_PROCBASED_CTLS,
> - msrs->procbased_ctls_low,
> - msrs->procbased_ctls_high);
> msrs->procbased_ctls_low =
> CPU_BASED_ALWAYSON_WITHOUT_TRUE_MSR;
> +
> + msrs->procbased_ctls_high = vmcs_conf->cpu_based_exec_ctrl;
> msrs->procbased_ctls_high &=
> CPU_BASED_INTR_WINDOW_EXITING |
> CPU_BASED_NMI_WINDOW_EXITING | CPU_BASED_USE_TSC_OFFSETTING |
> @@ -6675,12 +6676,9 @@ void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps)
> * depend on CPUID bits, they are added later by
> * vmx_vcpu_after_set_cpuid.
> */
> - if (msrs->procbased_ctls_high & CPU_BASED_ACTIVATE_SECONDARY_CONTROLS)
> - rdmsr(MSR_IA32_VMX_PROCBASED_CTLS2,
> - msrs->secondary_ctls_low,
> - msrs->secondary_ctls_high);
> -
> msrs->secondary_ctls_low = 0;
> +
> + msrs->secondary_ctls_high = vmcs_conf->cpu_based_2nd_exec_ctrl;
> msrs->secondary_ctls_high &=
> SECONDARY_EXEC_DESC |
> SECONDARY_EXEC_ENABLE_RDTSCP |
> diff --git a/arch/x86/kvm/vmx/nested.h b/arch/x86/kvm/vmx/nested.h
> index c92cea0b8ccc..fae047c6204b 100644
> --- a/arch/x86/kvm/vmx/nested.h
> +++ b/arch/x86/kvm/vmx/nested.h
> @@ -17,7 +17,7 @@ enum nvmx_vmentry_status {
> };
>
> void vmx_leave_nested(struct kvm_vcpu *vcpu);
> -void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps);
> +void nested_vmx_setup_ctls_msrs(struct vmcs_config *vmcs_conf, u32 ept_caps);
> void nested_vmx_hardware_unsetup(void);
> __init int nested_vmx_hardware_setup(int (*exit_handlers[])(struct kvm_vcpu *));
> void nested_vmx_set_vmcs_shadowing_bitmap(void);
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 5f7ef1f8d2c6..5d4158b7421c 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7310,7 +7310,7 @@ static int __init vmx_check_processor_compat(void)
> if (setup_vmcs_config(&vmcs_conf, &vmx_cap) < 0)
> return -EIO;
> if (nested)
> - nested_vmx_setup_ctls_msrs(&vmcs_conf.nested, vmx_cap.ept);
> + nested_vmx_setup_ctls_msrs(&vmcs_conf, vmx_cap.ept);
> if (memcmp(&vmcs_config, &vmcs_conf, sizeof(struct vmcs_config)) != 0) {
> printk(KERN_ERR "kvm: CPU %d feature inconsistency!\n",
> smp_processor_id());
> @@ -8285,8 +8285,7 @@ static __init int hardware_setup(void)
> setup_default_sgx_lepubkeyhash();
>
> if (nested) {
> - nested_vmx_setup_ctls_msrs(&vmcs_config.nested,
> - vmx_capability.ept);
> + nested_vmx_setup_ctls_msrs(&vmcs_config, vmx_capability.ept);
>
> r = nested_vmx_hardware_setup(kvm_vmx_exit_handlers);
> if (r)
> --
> 2.35.3
>
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