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    SubjectRe: [PATCH v6 25/25] KVM: nVMX: Enable CET support for nested guest
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    On Thu, 2023-09-14 at 02:33 -0400, Yang Weijiang wrote:
    > Set up CET MSRs, related VM_ENTRY/EXIT control bits and fixed CR4 setting
    > to enable CET for nested VM.
    >
    > Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
    > ---
    > arch/x86/kvm/vmx/nested.c | 27 +++++++++++++++++++++++++--
    > arch/x86/kvm/vmx/vmcs12.c | 6 ++++++
    > arch/x86/kvm/vmx/vmcs12.h | 14 +++++++++++++-
    > arch/x86/kvm/vmx/vmx.c | 2 ++
    > 4 files changed, 46 insertions(+), 3 deletions(-)
    >
    > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
    > index 78a3be394d00..2c4ff13fddb0 100644
    > --- a/arch/x86/kvm/vmx/nested.c
    > +++ b/arch/x86/kvm/vmx/nested.c
    > @@ -660,6 +660,28 @@ static inline bool nested_vmx_prepare_msr_bitmap(struct kvm_vcpu *vcpu,
    > nested_vmx_set_intercept_for_msr(vmx, msr_bitmap_l1, msr_bitmap_l0,
    > MSR_IA32_FLUSH_CMD, MSR_TYPE_W);
    >
    > + /* Pass CET MSRs to nested VM if L0 and L1 are set to pass-through. */
    > + nested_vmx_set_intercept_for_msr(vmx, msr_bitmap_l1, msr_bitmap_l0,
    > + MSR_IA32_U_CET, MSR_TYPE_RW);
    > +
    > + nested_vmx_set_intercept_for_msr(vmx, msr_bitmap_l1, msr_bitmap_l0,
    > + MSR_IA32_S_CET, MSR_TYPE_RW);
    > +
    > + nested_vmx_set_intercept_for_msr(vmx, msr_bitmap_l1, msr_bitmap_l0,
    > + MSR_IA32_PL0_SSP, MSR_TYPE_RW);
    > +
    > + nested_vmx_set_intercept_for_msr(vmx, msr_bitmap_l1, msr_bitmap_l0,
    > + MSR_IA32_PL1_SSP, MSR_TYPE_RW);
    > +
    > + nested_vmx_set_intercept_for_msr(vmx, msr_bitmap_l1, msr_bitmap_l0,
    > + MSR_IA32_PL2_SSP, MSR_TYPE_RW);
    > +
    > + nested_vmx_set_intercept_for_msr(vmx, msr_bitmap_l1, msr_bitmap_l0,
    > + MSR_IA32_PL3_SSP, MSR_TYPE_RW);
    > +
    > + nested_vmx_set_intercept_for_msr(vmx, msr_bitmap_l1, msr_bitmap_l0,
    > + MSR_IA32_INT_SSP_TAB, MSR_TYPE_RW);
    > +
    > kvm_vcpu_unmap(vcpu, &vmx->nested.msr_bitmap_map, false);
    >
    > vmx->nested.force_msr_bitmap_recalc = false;
    > @@ -6794,7 +6816,7 @@ static void nested_vmx_setup_exit_ctls(struct vmcs_config *vmcs_conf,
    > VM_EXIT_HOST_ADDR_SPACE_SIZE |
    > #endif
    > VM_EXIT_LOAD_IA32_PAT | VM_EXIT_SAVE_IA32_PAT |
    > - VM_EXIT_CLEAR_BNDCFGS;
    > + VM_EXIT_CLEAR_BNDCFGS | VM_EXIT_LOAD_CET_STATE;
    > msrs->exit_ctls_high |=
    > VM_EXIT_ALWAYSON_WITHOUT_TRUE_MSR |
    > VM_EXIT_LOAD_IA32_EFER | VM_EXIT_SAVE_IA32_EFER |
    > @@ -6816,7 +6838,8 @@ static void nested_vmx_setup_entry_ctls(struct vmcs_config *vmcs_conf,
    > #ifdef CONFIG_X86_64
    > VM_ENTRY_IA32E_MODE |
    > #endif
    > - VM_ENTRY_LOAD_IA32_PAT | VM_ENTRY_LOAD_BNDCFGS;
    > + VM_ENTRY_LOAD_IA32_PAT | VM_ENTRY_LOAD_BNDCFGS |
    > + VM_ENTRY_LOAD_CET_STATE;
    > msrs->entry_ctls_high |=
    > (VM_ENTRY_ALWAYSON_WITHOUT_TRUE_MSR | VM_ENTRY_LOAD_IA32_EFER |
    > VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL);
    > diff --git a/arch/x86/kvm/vmx/vmcs12.c b/arch/x86/kvm/vmx/vmcs12.c
    > index 106a72c923ca..4233b5ca9461 100644
    > --- a/arch/x86/kvm/vmx/vmcs12.c
    > +++ b/arch/x86/kvm/vmx/vmcs12.c
    > @@ -139,6 +139,9 @@ const unsigned short vmcs12_field_offsets[] = {
    > FIELD(GUEST_PENDING_DBG_EXCEPTIONS, guest_pending_dbg_exceptions),
    > FIELD(GUEST_SYSENTER_ESP, guest_sysenter_esp),
    > FIELD(GUEST_SYSENTER_EIP, guest_sysenter_eip),
    > + FIELD(GUEST_S_CET, guest_s_cet),
    > + FIELD(GUEST_SSP, guest_ssp),
    > + FIELD(GUEST_INTR_SSP_TABLE, guest_ssp_tbl),
    > FIELD(HOST_CR0, host_cr0),
    > FIELD(HOST_CR3, host_cr3),
    > FIELD(HOST_CR4, host_cr4),
    > @@ -151,5 +154,8 @@ const unsigned short vmcs12_field_offsets[] = {
    > FIELD(HOST_IA32_SYSENTER_EIP, host_ia32_sysenter_eip),
    > FIELD(HOST_RSP, host_rsp),
    > FIELD(HOST_RIP, host_rip),
    > + FIELD(HOST_S_CET, host_s_cet),
    > + FIELD(HOST_SSP, host_ssp),
    > + FIELD(HOST_INTR_SSP_TABLE, host_ssp_tbl),
    > };
    > const unsigned int nr_vmcs12_fields = ARRAY_SIZE(vmcs12_field_offsets);
    > diff --git a/arch/x86/kvm/vmx/vmcs12.h b/arch/x86/kvm/vmx/vmcs12.h
    > index 01936013428b..3884489e7f7e 100644
    > --- a/arch/x86/kvm/vmx/vmcs12.h
    > +++ b/arch/x86/kvm/vmx/vmcs12.h
    > @@ -117,7 +117,13 @@ struct __packed vmcs12 {
    > natural_width host_ia32_sysenter_eip;
    > natural_width host_rsp;
    > natural_width host_rip;
    > - natural_width paddingl[8]; /* room for future expansion */
    > + natural_width host_s_cet;
    > + natural_width host_ssp;
    > + natural_width host_ssp_tbl;
    > + natural_width guest_s_cet;
    > + natural_width guest_ssp;
    > + natural_width guest_ssp_tbl;
    > + natural_width paddingl[2]; /* room for future expansion */
    > u32 pin_based_vm_exec_control;
    > u32 cpu_based_vm_exec_control;
    > u32 exception_bitmap;
    > @@ -292,6 +298,12 @@ static inline void vmx_check_vmcs12_offsets(void)
    > CHECK_OFFSET(host_ia32_sysenter_eip, 656);
    > CHECK_OFFSET(host_rsp, 664);
    > CHECK_OFFSET(host_rip, 672);
    > + CHECK_OFFSET(host_s_cet, 680);
    > + CHECK_OFFSET(host_ssp, 688);
    > + CHECK_OFFSET(host_ssp_tbl, 696);
    > + CHECK_OFFSET(guest_s_cet, 704);
    > + CHECK_OFFSET(guest_ssp, 712);
    > + CHECK_OFFSET(guest_ssp_tbl, 720);
    > CHECK_OFFSET(pin_based_vm_exec_control, 744);
    > CHECK_OFFSET(cpu_based_vm_exec_control, 748);
    > CHECK_OFFSET(exception_bitmap, 752);
    > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
    > index f0dea8ecd0c6..2c43f1088d77 100644
    > --- a/arch/x86/kvm/vmx/vmx.c
    > +++ b/arch/x86/kvm/vmx/vmx.c
    > @@ -7731,6 +7731,8 @@ static void nested_vmx_cr_fixed1_bits_update(struct kvm_vcpu *vcpu)
    > cr4_fixed1_update(X86_CR4_PKE, ecx, feature_bit(PKU));
    > cr4_fixed1_update(X86_CR4_UMIP, ecx, feature_bit(UMIP));
    > cr4_fixed1_update(X86_CR4_LA57, ecx, feature_bit(LA57));
    > + cr4_fixed1_update(X86_CR4_CET, ecx, feature_bit(SHSTK));
    > + cr4_fixed1_update(X86_CR4_CET, edx, feature_bit(IBT));
    >
    > #undef cr4_fixed1_update
    > }


    It is surprising how little needs to be done to support the nested mode, but it does look correct.
    I might have missed something though, can't be 100% sure in this case.


    Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>

    Best regards,
    Maxim Levitsky






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