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Date: Thu, 7 Jan 2021 19:13:26 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: Tom Lendacky <thomas.lendacky@....com>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org, x86@...nel.org
Cc: Jim Mattson <jmattson@...gle.com>, Joerg Roedel <joro@...tes.org>,
Sean Christopherson <seanjc@...gle.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v5.1 27/34] KVM: SVM: Add support for booting APs in an
SEV-ES guest
On 04/01/21 21:20, Tom Lendacky wrote:
> From: Tom Lendacky <thomas.lendacky@....com>
>
> Typically under KVM, an AP is booted using the INIT-SIPI-SIPI sequence,
> where the guest vCPU register state is updated and then the vCPU is VMRUN
> to begin execution of the AP. For an SEV-ES guest, this won't work because
> the guest register state is encrypted.
>
> Following the GHCB specification, the hypervisor must not alter the guest
> register state, so KVM must track an AP/vCPU boot. Should the guest want
> to park the AP, it must use the AP Reset Hold exit event in place of, for
> example, a HLT loop.
>
> First AP boot (first INIT-SIPI-SIPI sequence):
> Execute the AP (vCPU) as it was initialized and measured by the SEV-ES
> support. It is up to the guest to transfer control of the AP to the
> proper location.
>
> Subsequent AP boot:
> KVM will expect to receive an AP Reset Hold exit event indicating that
> the vCPU is being parked and will require an INIT-SIPI-SIPI sequence to
> awaken it. When the AP Reset Hold exit event is received, KVM will place
> the vCPU into a simulated HLT mode. Upon receiving the INIT-SIPI-SIPI
> sequence, KVM will make the vCPU runnable. It is again up to the guest
> to then transfer control of the AP to the proper location.
>
> To differentiate between an actual HLT and an AP Reset Hold, a new MP
> state is introduced, KVM_MP_STATE_AP_RESET_HOLD, which the vCPU is
> placed in upon receiving the AP Reset Hold exit event. Additionally, to
> communicate the AP Reset Hold exit event up to userspace (if needed), a
> new exit reason is introduced, KVM_EXIT_AP_RESET_HOLD.
>
> A new x86 ops function is introduced, vcpu_deliver_sipi_vector, in order
> to accomplish AP booting. For VMX, vcpu_deliver_sipi_vector is set to the
> original SIPI delivery function, kvm_vcpu_deliver_sipi_vector(). SVM adds
> a new function that, for non SEV-ES guests, invokes the original SIPI
> delivery function, kvm_vcpu_deliver_sipi_vector(), but for SEV-ES guests,
> implements the logic above.
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
Queued, thanks.
Paolo
> ---
> arch/x86/include/asm/kvm_host.h | 3 +++
> arch/x86/kvm/lapic.c | 2 +-
> arch/x86/kvm/svm/sev.c | 22 ++++++++++++++++++++++
> arch/x86/kvm/svm/svm.c | 10 ++++++++++
> arch/x86/kvm/svm/svm.h | 2 ++
> arch/x86/kvm/vmx/vmx.c | 2 ++
> arch/x86/kvm/x86.c | 26 +++++++++++++++++++++-----
> include/uapi/linux/kvm.h | 2 ++
> 8 files changed, 63 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 39707e72b062..23d7b203c060 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1287,6 +1287,8 @@ struct kvm_x86_ops {
> void (*migrate_timers)(struct kvm_vcpu *vcpu);
> void (*msr_filter_changed)(struct kvm_vcpu *vcpu);
> int (*complete_emulated_msr)(struct kvm_vcpu *vcpu, int err);
> +
> + void (*vcpu_deliver_sipi_vector)(struct kvm_vcpu *vcpu, u8 vector);
> };
>
> struct kvm_x86_nested_ops {
> @@ -1468,6 +1470,7 @@ int kvm_fast_pio(struct kvm_vcpu *vcpu, int size, unsigned short port, int in);
> int kvm_emulate_cpuid(struct kvm_vcpu *vcpu);
> int kvm_emulate_halt(struct kvm_vcpu *vcpu);
> int kvm_vcpu_halt(struct kvm_vcpu *vcpu);
> +int kvm_emulate_ap_reset_hold(struct kvm_vcpu *vcpu);
> int kvm_emulate_wbinvd(struct kvm_vcpu *vcpu);
>
> void kvm_get_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg);
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 6a87623aa578..a2f08ed777d8 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -2898,7 +2898,7 @@ void kvm_apic_accept_events(struct kvm_vcpu *vcpu)
> /* evaluate pending_events before reading the vector */
> smp_rmb();
> sipi_vector = apic->sipi_vector;
> - kvm_vcpu_deliver_sipi_vector(vcpu, sipi_vector);
> + kvm_x86_ops.vcpu_deliver_sipi_vector(vcpu, sipi_vector);
> vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
> }
> }
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index e57847ff8bd2..a08cbc04cb4d 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1563,6 +1563,7 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
> goto vmgexit_err;
> break;
> case SVM_VMGEXIT_NMI_COMPLETE:
> + case SVM_VMGEXIT_AP_HLT_LOOP:
> case SVM_VMGEXIT_AP_JUMP_TABLE:
> case SVM_VMGEXIT_UNSUPPORTED_EVENT:
> break;
> @@ -1888,6 +1889,9 @@ int sev_handle_vmgexit(struct vcpu_svm *svm)
> case SVM_VMGEXIT_NMI_COMPLETE:
> ret = svm_invoke_exit_handler(svm, SVM_EXIT_IRET);
> break;
> + case SVM_VMGEXIT_AP_HLT_LOOP:
> + ret = kvm_emulate_ap_reset_hold(&svm->vcpu);
> + break;
> case SVM_VMGEXIT_AP_JUMP_TABLE: {
> struct kvm_sev_info *sev = &to_kvm_svm(svm->vcpu.kvm)->sev_info;
>
> @@ -2040,3 +2044,21 @@ void sev_es_vcpu_put(struct vcpu_svm *svm)
> wrmsrl(host_save_user_msrs[i].index, svm->host_user_msrs[i]);
> }
> }
> +
> +void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector)
> +{
> + struct vcpu_svm *svm = to_svm(vcpu);
> +
> + /* First SIPI: Use the values as initially set by the VMM */
> + if (!svm->received_first_sipi) {
> + svm->received_first_sipi = true;
> + return;
> + }
> +
> + /*
> + * Subsequent SIPI: Return from an AP Reset Hold VMGEXIT, where
> + * the guest will set the CS and RIP. Set SW_EXIT_INFO_2 to a
> + * non-zero value.
> + */
> + ghcb_set_sw_exit_info_2(svm->ghcb, 1);
> +}
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 941e5251e13f..5c37fa68ee56 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4382,6 +4382,14 @@ static bool svm_apic_init_signal_blocked(struct kvm_vcpu *vcpu)
> (vmcb_is_intercept(&svm->vmcb->control, INTERCEPT_INIT));
> }
>
> +static void svm_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector)
> +{
> + if (!sev_es_guest(vcpu->kvm))
> + return kvm_vcpu_deliver_sipi_vector(vcpu, vector);
> +
> + sev_vcpu_deliver_sipi_vector(vcpu, vector);
> +}
> +
> static void svm_vm_destroy(struct kvm *kvm)
> {
> avic_vm_destroy(kvm);
> @@ -4524,6 +4532,8 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
>
> .msr_filter_changed = svm_msr_filter_changed,
> .complete_emulated_msr = svm_complete_emulated_msr,
> +
> + .vcpu_deliver_sipi_vector = svm_vcpu_deliver_sipi_vector,
> };
>
> static struct kvm_x86_init_ops svm_init_ops __initdata = {
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index 5431e6335e2e..0fe874ae5498 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -185,6 +185,7 @@ struct vcpu_svm {
> struct vmcb_save_area *vmsa;
> struct ghcb *ghcb;
> struct kvm_host_map ghcb_map;
> + bool received_first_sipi;
>
> /* SEV-ES scratch area support */
> void *ghcb_sa;
> @@ -591,6 +592,7 @@ void sev_es_init_vmcb(struct vcpu_svm *svm);
> void sev_es_create_vcpu(struct vcpu_svm *svm);
> void sev_es_vcpu_load(struct vcpu_svm *svm, int cpu);
> void sev_es_vcpu_put(struct vcpu_svm *svm);
> +void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector);
>
> /* vmenter.S */
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 75c9c6a0a3a4..2af05d3b0590 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7707,6 +7707,8 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = {
> .msr_filter_changed = vmx_msr_filter_changed,
> .complete_emulated_msr = kvm_complete_insn_gp,
> .cpu_dirty_log_size = vmx_cpu_dirty_log_size,
> +
> + .vcpu_deliver_sipi_vector = kvm_vcpu_deliver_sipi_vector,
> };
>
> static __init int hardware_setup(void)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 648c677b12e9..660683a70b79 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7974,17 +7974,22 @@ void kvm_arch_exit(void)
> kmem_cache_destroy(x86_fpu_cache);
> }
>
> -int kvm_vcpu_halt(struct kvm_vcpu *vcpu)
> +int __kvm_vcpu_halt(struct kvm_vcpu *vcpu, int state, int reason)
> {
> ++vcpu->stat.halt_exits;
> if (lapic_in_kernel(vcpu)) {
> - vcpu->arch.mp_state = KVM_MP_STATE_HALTED;
> + vcpu->arch.mp_state = state;
> return 1;
> } else {
> - vcpu->run->exit_reason = KVM_EXIT_HLT;
> + vcpu->run->exit_reason = reason;
> return 0;
> }
> }
> +
> +int kvm_vcpu_halt(struct kvm_vcpu *vcpu)
> +{
> + return __kvm_vcpu_halt(vcpu, KVM_MP_STATE_HALTED, KVM_EXIT_HLT);
> +}
> EXPORT_SYMBOL_GPL(kvm_vcpu_halt);
>
> int kvm_emulate_halt(struct kvm_vcpu *vcpu)
> @@ -7998,6 +8003,14 @@ int kvm_emulate_halt(struct kvm_vcpu *vcpu)
> }
> EXPORT_SYMBOL_GPL(kvm_emulate_halt);
>
> +int kvm_emulate_ap_reset_hold(struct kvm_vcpu *vcpu)
> +{
> + int ret = kvm_skip_emulated_instruction(vcpu);
> +
> + return __kvm_vcpu_halt(vcpu, KVM_MP_STATE_AP_RESET_HOLD, KVM_EXIT_AP_RESET_HOLD) && ret;
> +}
> +EXPORT_SYMBOL_GPL(kvm_emulate_ap_reset_hold);
> +
> #ifdef CONFIG_X86_64
> static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
> unsigned long clock_type)
> @@ -9092,6 +9105,7 @@ static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu)
> kvm_apic_accept_events(vcpu);
> switch(vcpu->arch.mp_state) {
> case KVM_MP_STATE_HALTED:
> + case KVM_MP_STATE_AP_RESET_HOLD:
> vcpu->arch.pv.pv_unhalted = false;
> vcpu->arch.mp_state =
> KVM_MP_STATE_RUNNABLE;
> @@ -9518,8 +9532,9 @@ int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
> kvm_load_guest_fpu(vcpu);
>
> kvm_apic_accept_events(vcpu);
> - if (vcpu->arch.mp_state == KVM_MP_STATE_HALTED &&
> - vcpu->arch.pv.pv_unhalted)
> + if ((vcpu->arch.mp_state == KVM_MP_STATE_HALTED ||
> + vcpu->arch.mp_state == KVM_MP_STATE_AP_RESET_HOLD) &&
> + vcpu->arch.pv.pv_unhalted)
> mp_state->mp_state = KVM_MP_STATE_RUNNABLE;
> else
> mp_state->mp_state = vcpu->arch.mp_state;
> @@ -10150,6 +10165,7 @@ void kvm_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector)
> kvm_set_segment(vcpu, &cs, VCPU_SREG_CS);
> kvm_rip_write(vcpu, 0);
> }
> +EXPORT_SYMBOL_GPL(kvm_vcpu_deliver_sipi_vector);
>
> int kvm_arch_hardware_enable(void)
> {
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 886802b8ffba..374c67875cdb 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -251,6 +251,7 @@ struct kvm_hyperv_exit {
> #define KVM_EXIT_X86_RDMSR 29
> #define KVM_EXIT_X86_WRMSR 30
> #define KVM_EXIT_DIRTY_RING_FULL 31
> +#define KVM_EXIT_AP_RESET_HOLD 32
>
> /* For KVM_EXIT_INTERNAL_ERROR */
> /* Emulate instruction failed. */
> @@ -573,6 +574,7 @@ struct kvm_vapic_addr {
> #define KVM_MP_STATE_CHECK_STOP 6
> #define KVM_MP_STATE_OPERATING 7
> #define KVM_MP_STATE_LOAD 8
> +#define KVM_MP_STATE_AP_RESET_HOLD 9
>
> struct kvm_mp_state {
> __u32 mp_state;
>
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