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    Subject[PATCH v4] X86/KVM: Properly update 'tsc_offset' to represent the running guest
    Date
    Update 'tsc_offset' on vmentry/vmexit of L2 guests to ensure that it always
    captures the TSC_OFFSET of the running guest whether it is the L1 or L2
    guest.

    Cc: Jim Mattson <jmattson@google.com>
    Cc: Paolo Bonzini <pbonzini@redhat.com>
    Cc: Radim Krčmář <rkrcmar@redhat.com>
    Cc: kvm@vger.kernel.org
    Cc: linux-kernel@vger.kernel.org
    Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
    [AMD changes, fix update_ia32_tsc_adjust_msr. - Paolo]
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

    ---
    v3 -> v4:
    - Restore L01 tsc_offset on enter_vmx_non_root_mode failures.
    - Move tsc_offset update for L02 later in nested_vmx_run.

    v2 -> v3:
    - Add AMD bits as well.
    - Fix update_ia32_tsc_adjust_msr.

    v1 -> v2:
    - Rewrote the patch to always update tsc_offset to represent the current
    guest (pbonzini@)
    ---
    arch/x86/include/asm/kvm_host.h | 1 +
    arch/x86/kvm/svm.c | 17 ++++++++++++++++-
    arch/x86/kvm/vmx.c | 29 ++++++++++++++++++++++++-----
    arch/x86/kvm/x86.c | 6 ++++--
    4 files changed, 45 insertions(+), 8 deletions(-)

    diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    index 7a200f6..a40a32e 100644
    --- a/arch/x86/include/asm/kvm_host.h
    +++ b/arch/x86/include/asm/kvm_host.h
    @@ -1016,6 +1016,7 @@ struct kvm_x86_ops {

    bool (*has_wbinvd_exit)(void);

    + u64 (*read_l1_tsc_offset)(struct kvm_vcpu *vcpu);
    void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset);

    void (*get_exit_info)(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2);
    diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
    index b58787d..1f00c18 100644
    --- a/arch/x86/kvm/svm.c
    +++ b/arch/x86/kvm/svm.c
    @@ -1423,12 +1423,23 @@ static void init_sys_seg(struct vmcb_seg *seg, uint32_t type)
    seg->base = 0;
    }

    +static u64 svm_read_l1_tsc_offset(struct kvm_vcpu *vcpu)
    +{
    + struct vcpu_svm *svm = to_svm(vcpu);
    +
    + if (is_guest_mode(vcpu))
    + return svm->nested.hsave->control.tsc_offset;
    +
    + return vcpu->arch.tsc_offset;
    +}
    +
    static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
    {
    struct vcpu_svm *svm = to_svm(vcpu);
    u64 g_tsc_offset = 0;

    if (is_guest_mode(vcpu)) {
    + /* Write L1's TSC offset. */
    g_tsc_offset = svm->vmcb->control.tsc_offset -
    svm->nested.hsave->control.tsc_offset;
    svm->nested.hsave->control.tsc_offset = offset;
    @@ -3322,6 +3333,7 @@ static int nested_svm_vmexit(struct vcpu_svm *svm)
    /* Restore the original control entries */
    copy_vmcb_control_area(vmcb, hsave);

    + vcpu->arch.tsc_offset = svm->vmcb->control.tsc_offset;
    kvm_clear_exception_queue(&svm->vcpu);
    kvm_clear_interrupt_queue(&svm->vcpu);

    @@ -3482,10 +3494,12 @@ static void enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb_gpa,
    /* We don't want to see VMMCALLs from a nested guest */
    clr_intercept(svm, INTERCEPT_VMMCALL);

    + vcpu->arch.tsc_offset += nested_vmcb->control.tsc_offset;
    + svm->vmcb->control.tsc_offset = vcpu->arch.tsc_offset;
    +
    svm->vmcb->control.virt_ext = nested_vmcb->control.virt_ext;
    svm->vmcb->control.int_vector = nested_vmcb->control.int_vector;
    svm->vmcb->control.int_state = nested_vmcb->control.int_state;
    - svm->vmcb->control.tsc_offset += nested_vmcb->control.tsc_offset;
    svm->vmcb->control.event_inj = nested_vmcb->control.event_inj;
    svm->vmcb->control.event_inj_err = nested_vmcb->control.event_inj_err;

    @@ -7102,6 +7116,7 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {

    .has_wbinvd_exit = svm_has_wbinvd_exit,

    + .read_l1_tsc_offset = svm_read_l1_tsc_offset,
    .write_tsc_offset = svm_write_tsc_offset,

    .set_tdp_cr3 = set_tdp_cr3,
    diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
    index b6942de..05ba3c6 100644
    --- a/arch/x86/kvm/vmx.c
    +++ b/arch/x86/kvm/vmx.c
    @@ -2885,6 +2885,17 @@ static void setup_msrs(struct vcpu_vmx *vmx)
    vmx_update_msr_bitmap(&vmx->vcpu);
    }

    +static u64 vmx_read_l1_tsc_offset(struct kvm_vcpu *vcpu)
    +{
    + struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
    +
    + if (is_guest_mode(vcpu) &&
    + (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING))
    + return vcpu->arch.tsc_offset - vmcs12->tsc_offset;
    +
    + return vcpu->arch.tsc_offset;
    +}
    +
    /*
    * reads and returns guest's timestamp counter "register"
    * guest_tsc = (host_tsc * tsc multiplier) >> 48 + tsc_offset
    @@ -11112,11 +11123,8 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
    vmcs_write64(GUEST_IA32_PAT, vmx->vcpu.arch.pat);
    }

    - if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
    - vmcs_write64(TSC_OFFSET,
    - vcpu->arch.tsc_offset + vmcs12->tsc_offset);
    - else
    - vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset);
    + vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset);
    +
    if (kvm_has_tsc_control)
    decache_tsc_multiplier(vmx);

    @@ -11366,6 +11374,8 @@ static int enter_vmx_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
    vmx_segment_cache_clear(vmx);

    if (prepare_vmcs02(vcpu, vmcs12, from_vmentry, &exit_qual)) {
    + if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
    + vcpu->arch.tsc_offset -= vmcs12->tsc_offset;
    leave_guest_mode(vcpu);
    vmx_switch_vmcs(vcpu, &vmx->vmcs01);
    nested_vmx_entry_failure(vcpu, vmcs12,
    @@ -11377,6 +11387,8 @@ static int enter_vmx_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
    vmcs12->vm_entry_msr_load_addr,
    vmcs12->vm_entry_msr_load_count);
    if (msr_entry_idx) {
    + if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
    + vcpu->arch.tsc_offset -= vmcs12->tsc_offset;
    leave_guest_mode(vcpu);
    vmx_switch_vmcs(vcpu, &vmx->vmcs01);
    nested_vmx_entry_failure(vcpu, vmcs12,
    @@ -11461,6 +11473,9 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
    return 1;
    }

    + if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
    + vcpu->arch.tsc_offset += vmcs12->tsc_offset;
    +
    /*
    * We're finally done with prerequisite checking, and can start with
    * the nested entry.
    @@ -11964,6 +11979,9 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,

    leave_guest_mode(vcpu);

    + if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
    + vcpu->arch.tsc_offset -= vmcs12->tsc_offset;
    +
    if (likely(!vmx->fail)) {
    if (exit_reason == -1)
    sync_vmcs12(vcpu, vmcs12);
    @@ -12801,6 +12819,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = {

    .has_wbinvd_exit = cpu_has_vmx_wbinvd_exit,

    + .read_l1_tsc_offset = vmx_read_l1_tsc_offset,
    .write_tsc_offset = vmx_write_tsc_offset,

    .set_tdp_cr3 = vmx_set_cr3,
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index 7846a8a..2f83cb2 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -1490,7 +1490,7 @@ static void kvm_track_tsc_matching(struct kvm_vcpu *vcpu)

    static void update_ia32_tsc_adjust_msr(struct kvm_vcpu *vcpu, s64 offset)
    {
    - u64 curr_offset = vcpu->arch.tsc_offset;
    + u64 curr_offset = kvm_x86_ops->read_l1_tsc_offset(vcpu);
    vcpu->arch.ia32_tsc_adjust_msr += offset - curr_offset;
    }

    @@ -1532,7 +1532,9 @@ static u64 kvm_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc)

    u64 kvm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)
    {
    - return vcpu->arch.tsc_offset + kvm_scale_tsc(vcpu, host_tsc);
    + u64 tsc_offset = kvm_x86_ops->read_l1_tsc_offset(vcpu);
    +
    + return tsc_offset + kvm_scale_tsc(vcpu, host_tsc);
    }
    EXPORT_SYMBOL_GPL(kvm_read_l1_tsc);

    --
    2.7.4
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