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    Subject[PATCH v7 21/39] KVM: nVMX: hyper-v: Enable L2 TLB flush
    Date
    Enable L2 TLB flush feature on nVMX when:
    - Enlightened VMCS is in use.
    - The feature flag is enabled in eVMCS.
    - The feature flag is enabled in partition assist page.

    Perform synthetic vmexit to L1 after processing TLB flush call upon
    request (HV_VMX_SYNTHETIC_EXIT_REASON_TRAP_AFTER_FLUSH).

    Note: nested_evmcs_l2_tlb_flush_enabled() uses cached VP assist page copy
    which gets updated from nested_vmx_handle_enlightened_vmptrld(). This is
    also guaranteed to happen post migration with eVMCS backed L2 running.

    Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
    Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
    ---
    arch/x86/kvm/vmx/evmcs.c | 17 +++++++++++++++++
    arch/x86/kvm/vmx/evmcs.h | 10 ++++++++++
    arch/x86/kvm/vmx/nested.c | 22 ++++++++++++++++++++++
    3 files changed, 49 insertions(+)

    diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c
    index 7cd7b16942c6..870de69172be 100644
    --- a/arch/x86/kvm/vmx/evmcs.c
    +++ b/arch/x86/kvm/vmx/evmcs.c
    @@ -6,6 +6,7 @@
    #include "../hyperv.h"
    #include "../cpuid.h"
    #include "evmcs.h"
    +#include "nested.h"
    #include "vmcs.h"
    #include "vmx.h"
    #include "trace.h"
    @@ -433,6 +434,22 @@ int nested_enable_evmcs(struct kvm_vcpu *vcpu,
    return 0;
    }

    +bool nested_evmcs_l2_tlb_flush_enabled(struct kvm_vcpu *vcpu)
    +{
    + struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
    + struct vcpu_vmx *vmx = to_vmx(vcpu);
    + struct hv_enlightened_vmcs *evmcs = vmx->nested.hv_evmcs;
    +
    + if (!hv_vcpu || !evmcs)
    + return false;
    +
    + if (!evmcs->hv_enlightenments_control.nested_flush_hypercall)
    + return false;
    +
    + return hv_vcpu->vp_assist_page.nested_control.features.directhypercall;
    +}
    +
    void vmx_hv_inject_synthetic_vmexit_post_tlb_flush(struct kvm_vcpu *vcpu)
    {
    + nested_vmx_vmexit(vcpu, HV_VMX_SYNTHETIC_EXIT_REASON_TRAP_AFTER_FLUSH, 0, 0);
    }
    diff --git a/arch/x86/kvm/vmx/evmcs.h b/arch/x86/kvm/vmx/evmcs.h
    index 22d238b36238..0267b6191e6c 100644
    --- a/arch/x86/kvm/vmx/evmcs.h
    +++ b/arch/x86/kvm/vmx/evmcs.h
    @@ -66,6 +66,15 @@ DECLARE_STATIC_KEY_FALSE(enable_evmcs);
    #define EVMCS1_UNSUPPORTED_VMENTRY_CTRL (VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL)
    #define EVMCS1_UNSUPPORTED_VMFUNC (VMX_VMFUNC_EPTP_SWITCHING)

    +/*
    + * Note, Hyper-V isn't actually stealing bit 28 from Intel, just abusing it by
    + * pairing it with architecturally impossible exit reasons. Bit 28 is set only
    + * on SMI exits to a SMI transfer monitor (STM) and if and only if a MTF VM-Exit
    + * is pending. I.e. it will never be set by hardware for non-SMI exits (there
    + * are only three), nor will it ever be set unless the VMM is an STM.
    + */
    +#define HV_VMX_SYNTHETIC_EXIT_REASON_TRAP_AFTER_FLUSH 0x10000031
    +
    struct evmcs_field {
    u16 offset;
    u16 clean_field;
    @@ -245,6 +254,7 @@ int nested_enable_evmcs(struct kvm_vcpu *vcpu,
    uint16_t *vmcs_version);
    void nested_evmcs_filter_control_msr(u32 msr_index, u64 *pdata);
    int nested_evmcs_check_controls(struct vmcs12 *vmcs12);
    +bool nested_evmcs_l2_tlb_flush_enabled(struct kvm_vcpu *vcpu);
    void vmx_hv_inject_synthetic_vmexit_post_tlb_flush(struct kvm_vcpu *vcpu);

    #endif /* __KVM_X86_VMX_EVMCS_H */
    diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
    index 87bff81f7f3e..69d06f77d7b4 100644
    --- a/arch/x86/kvm/vmx/nested.c
    +++ b/arch/x86/kvm/vmx/nested.c
    @@ -1170,6 +1170,17 @@ static void nested_vmx_transition_tlb_flush(struct kvm_vcpu *vcpu,
    {
    struct vcpu_vmx *vmx = to_vmx(vcpu);

    + /*
    + * KVM_REQ_HV_TLB_FLUSH flushes entries from either L1's VP_ID or
    + * L2's VP_ID upon request from the guest. Make sure we check for
    + * pending entries for the case when the request got misplaced (e.g.
    + * a transition from L2->L1 happened while processing L2 TLB flush
    + * request or vice versa). kvm_hv_vcpu_flush_tlb() will not flush
    + * anything if there are no requests in the corresponding buffer.
    + */
    + if (to_hv_vcpu(vcpu))
    + kvm_make_request(KVM_REQ_HV_TLB_FLUSH, vcpu);
    +
    /*
    * If vmcs12 doesn't use VPID, L1 expects linear and combined mappings
    * for *all* contexts to be flushed on VM-Enter/VM-Exit, i.e. it's a
    @@ -3278,6 +3289,12 @@ static bool nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)

    static bool vmx_get_nested_state_pages(struct kvm_vcpu *vcpu)
    {
    + /*
    + * Note: nested_get_evmcs_page() also updates 'vp_assist_page' copy
    + * in 'struct kvm_vcpu_hv' in case eVMCS is in use, this is mandatory
    + * to make nested_evmcs_l2_tlb_flush_enabled() work correctly post
    + * migration.
    + */
    if (!nested_get_evmcs_page(vcpu)) {
    pr_debug_ratelimited("%s: enlightened vmptrld failed\n",
    __func__);
    @@ -6007,6 +6024,11 @@ static bool nested_vmx_l0_wants_exit(struct kvm_vcpu *vcpu,
    * Handle L2's bus locks in L0 directly.
    */
    return true;
    + case EXIT_REASON_VMCALL:
    + /* Hyper-V L2 TLB flush hypercall is handled by L0 */
    + return guest_hv_cpuid_has_l2_tlb_flush(vcpu) &&
    + nested_evmcs_l2_tlb_flush_enabled(vcpu) &&
    + kvm_hv_is_tlb_flush_hcall(vcpu);
    default:
    break;
    }
    --
    2.35.3
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