Re: [PATCH v3] KVM: nVMX: Sync L2 guest CET states between L1/L2

Paolo Bonzini
2021-03-03T17:11:36Z

On 03/03/21 07:04, Yang Weijiang wrote:
> These fields are rarely updated by L1 QEMU/KVM, sync them when L1 is trying to
> read/write them and after they're changed. If CET guest entry-load bit is not
> set by L1 guest, migrate them to L2 manaully.
>
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>

Hi Weijiang, can you post the complete series again? Thanks!

Paolo

> ---
> arch/x86/kvm/cpuid.c | 1 -
> arch/x86/kvm/vmx/nested.c | 30 ++++++++++++++++++++++++++++++
> arch/x86/kvm/vmx/vmx.h | 3 +++
> 3 files changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index d191de769093..8692f53b8cd0 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -143,7 +143,6 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
> }
> vcpu->arch.guest_supported_xss =
> (((u64)best->edx << 32) | best->ecx) & supported_xss;
> -
> } else {
> vcpu->arch.guest_supported_xss = 0;
> }
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 9728efd529a1..24cace55e1f9 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -2516,6 +2516,13 @@ static void prepare_vmcs02_rare(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
> vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, vmx->msr_autoload.guest.nr);
>
> set_cr4_guest_host_mask(vmx);
> +
> + if (kvm_cet_supported() && vmx->nested.nested_run_pending &&
> + (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE)) {
> + vmcs_writel(GUEST_SSP, vmcs12->guest_ssp);
> + vmcs_writel(GUEST_S_CET, vmcs12->guest_s_cet);
> + vmcs_writel(GUEST_INTR_SSP_TABLE, vmcs12->guest_ssp_tbl);
> + }
> }
>
> /*
> @@ -2556,6 +2563,15 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
> if (kvm_mpx_supported() && (!vmx->nested.nested_run_pending ||
> !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS)))
> vmcs_write64(GUEST_BNDCFGS, vmx->nested.vmcs01_guest_bndcfgs);
> +
> + if (kvm_cet_supported() && (!vmx->nested.nested_run_pending ||
> + !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE))) {
> + vmcs_writel(GUEST_SSP, vmx->nested.vmcs01_guest_ssp);
> + vmcs_writel(GUEST_S_CET, vmx->nested.vmcs01_guest_s_cet);
> + vmcs_writel(GUEST_INTR_SSP_TABLE,
> + vmx->nested.vmcs01_guest_ssp_tbl);
> + }
> +
> vmx_set_rflags(vcpu, vmcs12->guest_rflags);
>
> /* EXCEPTION_BITMAP and CR0_GUEST_HOST_MASK should basically be the
> @@ -3375,6 +3391,12 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
> if (kvm_mpx_supported() &&
> !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_BNDCFGS))
> vmx->nested.vmcs01_guest_bndcfgs = vmcs_read64(GUEST_BNDCFGS);
> + if (kvm_cet_supported() &&
> + !(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE)) {
> + vmx->nested.vmcs01_guest_ssp = vmcs_readl(GUEST_SSP);
> + vmx->nested.vmcs01_guest_s_cet = vmcs_readl(GUEST_S_CET);
> + vmx->nested.vmcs01_guest_ssp_tbl = vmcs_readl(GUEST_INTR_SSP_TABLE);
> + }
>
> /*
> * Overwrite vmcs01.GUEST_CR3 with L1's CR3 if EPT is disabled *and*
> @@ -4001,6 +4023,9 @@ static bool is_vmcs12_ext_field(unsigned long field)
> case GUEST_IDTR_BASE:
> case GUEST_PENDING_DBG_EXCEPTIONS:
> case GUEST_BNDCFGS:
> + case GUEST_SSP:
> + case GUEST_INTR_SSP_TABLE:
> + case GUEST_S_CET:
> return true;
> default:
> break;
> @@ -4052,6 +4077,11 @@ static void sync_vmcs02_to_vmcs12_rare(struct kvm_vcpu *vcpu,
> vmcs_readl(GUEST_PENDING_DBG_EXCEPTIONS);
> if (kvm_mpx_supported())
> vmcs12->guest_bndcfgs = vmcs_read64(GUEST_BNDCFGS);
> + if (kvm_cet_supported()) {
> + vmcs12->guest_ssp = vmcs_readl(GUEST_SSP);
> + vmcs12->guest_s_cet = vmcs_readl(GUEST_S_CET);
> + vmcs12->guest_ssp_tbl = vmcs_readl(GUEST_INTR_SSP_TABLE);
> + }
>
> vmx->nested.need_sync_vmcs02_to_vmcs12_rare = false;
> }
> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index 9d3a557949ac..36dc4fdb0909 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -155,6 +155,9 @@ struct nested_vmx {
> /* to migrate it to L2 if VM_ENTRY_LOAD_DEBUG_CONTROLS is off */
> u64 vmcs01_debugctl;
> u64 vmcs01_guest_bndcfgs;
> + u64 vmcs01_guest_ssp;
> + u64 vmcs01_guest_s_cet;
> + u64 vmcs01_guest_ssp_tbl;
>
> /* to migrate it to L1 if L2 writes to L1's CR8 directly */
> int l1_tpr_threshold;
>