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    Subject[RFC PATCH v3 09/10] KVM: VMX: Advertise MITI_CTRL_BHB_CLEAR_SEQ_S_SUPPORT
    Date
    From: Zhang Chen <chen.zhang@intel.com>

    Allow guest to report if the short BHB-clearing sequence is in use.

    KVM will deploy BHI_DIS_S for the guest if the short BHB-clearing
    sequence is in use and the processor doesn't enumerate BHI_NO.

    Signed-off-by: Zhang Chen <chen.zhang@intel.com>
    Signed-off-by: Chao Gao <chao.gao@intel.com>
    ---
    arch/x86/kvm/vmx/vmx.c | 31 ++++++++++++++++++++++++++++---
    1 file changed, 28 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
    index cc260b14f8df..c5ceaebd954b 100644
    --- a/arch/x86/kvm/vmx/vmx.c
    +++ b/arch/x86/kvm/vmx/vmx.c
    @@ -1956,8 +1956,8 @@ static inline bool is_vmx_feature_control_msr_valid(struct vcpu_vmx *vmx,
    }

    #define VIRTUAL_ENUMERATION_VALID_BITS VIRT_ENUM_MITIGATION_CTRL_SUPPORT
    -#define MITI_ENUM_VALID_BITS 0ULL
    -#define MITI_CTRL_VALID_BITS 0ULL
    +#define MITI_ENUM_VALID_BITS MITI_ENUM_BHB_CLEAR_SEQ_S_SUPPORT
    +#define MITI_CTRL_VALID_BITS MITI_CTRL_BHB_CLEAR_SEQ_S_USED

    static int vmx_get_msr_feature(struct kvm_msr_entry *msr)
    {
    @@ -2204,7 +2204,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
    struct vmx_uret_msr *msr;
    int ret = 0;
    u32 msr_index = msr_info->index;
    - u64 data = msr_info->data;
    + u64 data = msr_info->data, spec_ctrl_mask = 0;
    u32 index;

    switch (msr_index) {
    @@ -2508,6 +2508,31 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
    if (data & ~MITI_CTRL_VALID_BITS)
    return 1;

    + if (data & MITI_CTRL_BHB_CLEAR_SEQ_S_USED &&
    + kvm_cpu_cap_has(X86_FEATURE_BHI_CTRL) &&
    + !(host_arch_capabilities & ARCH_CAP_BHI_NO))
    + spec_ctrl_mask |= SPEC_CTRL_BHI_DIS_S;
    +
    + /*
    + * Intercept IA32_SPEC_CTRL to disallow guest from changing
    + * certain bits if "virtualize IA32_SPEC_CTRL" isn't supported
    + * e.g., in nested case.
    + */
    + if (spec_ctrl_mask && !cpu_has_spec_ctrl_shadow())
    + vmx_enable_intercept_for_msr(vcpu, MSR_IA32_SPEC_CTRL, MSR_TYPE_RW);
    +
    + /*
    + * KVM_CAP_FORCE_SPEC_CTRL takes precedence over
    + * MSR_VIRTUAL_MITIGATION_CTRL.
    + */
    + spec_ctrl_mask &= ~vmx->vcpu.kvm->arch.force_spec_ctrl_mask;
    +
    + vmx->force_spec_ctrl_mask = vmx->vcpu.kvm->arch.force_spec_ctrl_mask |
    + spec_ctrl_mask;
    + vmx->force_spec_ctrl_value = vmx->vcpu.kvm->arch.force_spec_ctrl_value |
    + spec_ctrl_mask;
    + vmx_set_spec_ctrl(&vmx->vcpu, vmx->spec_ctrl_shadow);
    +
    vmx->msr_virtual_mitigation_ctrl = data;
    break;
    default:
    --
    2.39.3

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