Re: [PATCH v19 087/130] KVM: TDX: handle vcpu migration over logical processor

Binbin Wu
2024-04-07T09:03:32Z

On 2/26/2024 4:26 PM, isaku.yamahata@intel.com wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> For vcpu migration, in the case of VMX, VMCS is flushed on the source pcpu,
> and load it on the target pcpu. There are corresponding TDX SEAMCALL APIs,
> call them on vcpu migration. The logic is mostly same as VMX except the
> TDX SEAMCALLs are used.
>
> When shutting down the machine,

"the machine" -> "a VM"

> (VMX or TDX) vcpus needs to be shutdown on
^
need
> each pcpu. Do the similar for TDX with TDX SEAMCALL APIs.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> arch/x86/kvm/vmx/main.c | 32 ++++++-
> arch/x86/kvm/vmx/tdx.c | 190 ++++++++++++++++++++++++++++++++++++-
> arch/x86/kvm/vmx/tdx.h | 2 +
> arch/x86/kvm/vmx/x86_ops.h | 4 +
> 4 files changed, 221 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index 8275a242ce07..9b336c1a6508 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -33,6 +33,14 @@ static int vt_max_vcpus(struct kvm *kvm)
> static int vt_flush_remote_tlbs(struct kvm *kvm);
> #endif
>
> +static void vt_hardware_disable(void)
> +{
> + /* Note, TDX *and* VMX need to be disabled if TDX is enabled. */
> + if (enable_tdx)
> + tdx_hardware_disable();
> + vmx_hardware_disable();
> +}
> +
> static __init int vt_hardware_setup(void)
> {
> int ret;
> @@ -201,6 +209,16 @@ static fastpath_t vt_vcpu_run(struct kvm_vcpu *vcpu)
> return vmx_vcpu_run(vcpu);
> }
>
> +static void vt_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> +{
> + if (is_td_vcpu(vcpu)) {
> + tdx_vcpu_load(vcpu, cpu);
> + return;
> + }
> +
> + vmx_vcpu_load(vcpu, cpu);
> +}
> +
> static void vt_flush_tlb_all(struct kvm_vcpu *vcpu)
> {
> if (is_td_vcpu(vcpu)) {
> @@ -262,6 +280,14 @@ static void vt_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa,
> vmx_load_mmu_pgd(vcpu, root_hpa, pgd_level);
> }
>
> +static void vt_sched_in(struct kvm_vcpu *vcpu, int cpu)
> +{
> + if (is_td_vcpu(vcpu))
> + return;
> +
> + vmx_sched_in(vcpu, cpu);
> +}
> +
> static u8 vt_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
> {
> if (is_td_vcpu(vcpu))
> @@ -335,7 +361,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
>
> /* TDX cpu enablement is done by tdx_hardware_setup(). */
> .hardware_enable = vmx_hardware_enable,
> - .hardware_disable = vmx_hardware_disable,
> + .hardware_disable = vt_hardware_disable,
> .has_emulated_msr = vmx_has_emulated_msr,
>
> .is_vm_type_supported = vt_is_vm_type_supported,
> @@ -353,7 +379,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
> .vcpu_reset = vt_vcpu_reset,
>
> .prepare_switch_to_guest = vt_prepare_switch_to_guest,
> - .vcpu_load = vmx_vcpu_load,
> + .vcpu_load = vt_vcpu_load,
> .vcpu_put = vt_vcpu_put,
>
> .update_exception_bitmap = vmx_update_exception_bitmap,
> @@ -440,7 +466,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
>
> .request_immediate_exit = vmx_request_immediate_exit,
>
> - .sched_in = vmx_sched_in,
> + .sched_in = vt_sched_in,
>
> .cpu_dirty_log_size = PML_ENTITY_NUM,
> .update_cpu_dirty_logging = vmx_update_cpu_dirty_logging,
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index ad4d3d4eaf6c..7aa9188f384d 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -106,6 +106,14 @@ static DEFINE_MUTEX(tdx_lock);
> static struct mutex *tdx_mng_key_config_lock;
> static atomic_t nr_configured_hkid;
>
> +/*
> + * A per-CPU list of TD vCPUs associated with a given CPU. Used when a CPU
> + * is brought down

Not necessarily to be a CPU brought down.
It will also be triggered by the last VM being destroyed.

But had a seond thought, if it is trigged by the last VM case, the list
should be empty already.
So I am OK with the descripton.

> to invoke TDH_VP_FLUSH on the approapriate TD vCPUS.

"approapriate" -> "appropriate"

> + * Protected by interrupt mask. This list is manipulated in process context
> + * of vcpu and IPI callback. See tdx_flush_vp_on_cpu().
> + */
> +static DEFINE_PER_CPU(struct list_head, associated_tdvcpus);
> +
> static __always_inline hpa_t set_hkid_to_hpa(hpa_t pa, u16 hkid)
> {
> return pa | ((hpa_t)hkid << boot_cpu_data.x86_phys_bits);
> @@ -138,6 +146,37 @@ static inline bool is_td_finalized(struct kvm_tdx *kvm_tdx)
> return kvm_tdx->finalized;
> }
>
> +static inline void tdx_disassociate_vp(struct kvm_vcpu *vcpu)
> +{
> + lockdep_assert_irqs_disabled();
> +
> + list_del(&to_tdx(vcpu)->cpu_list);
> +
> + /*
> + * Ensure tdx->cpu_list is updated is before setting vcpu->cpu to -1,
> + * otherwise, a different CPU can see vcpu->cpu = -1 and add the vCPU
> + * to its list before its deleted from this CPUs list.
> + */
> + smp_wmb();
> +
> + vcpu->cpu = -1;
> +}
> +
> +static void tdx_disassociate_vp_arg(void *vcpu)
> +{
> + tdx_disassociate_vp(vcpu);
> +}
> +
> +static void tdx_disassociate_vp_on_cpu(struct kvm_vcpu *vcpu)
> +{
> + int cpu = vcpu->cpu;
> +
> + if (unlikely(cpu == -1))
> + return;
> +
> + smp_call_function_single(cpu, tdx_disassociate_vp_arg, vcpu, 1);
> +}
> +
> static void tdx_clear_page(unsigned long page_pa)
> {
> const void *zero_page = (const void *) __va(page_to_phys(ZERO_PAGE(0)));
> @@ -218,6 +257,87 @@ static void tdx_reclaim_control_page(unsigned long td_page_pa)
> free_page((unsigned long)__va(td_page_pa));
> }
>
> +struct tdx_flush_vp_arg {
> + struct kvm_vcpu *vcpu;
> + u64 err;
> +};
> +
> +static void tdx_flush_vp(void *arg_)

It is more common to use "_arg" instead of "arg_".

> +{
> + struct tdx_flush_vp_arg *arg = arg_;
> + struct kvm_vcpu *vcpu = arg->vcpu;
> + u64 err;
> +
> + arg->err = 0;
> + lockdep_assert_irqs_disabled();
> +
> + /* Task migration can race with CPU offlining. */
> + if (unlikely(vcpu->cpu != raw_smp_processor_id()))
> + return;
> +
> + /*
> + * No need to do TDH_VP_FLUSH if the vCPU hasn't been initialized. The
> + * list tracking still needs to be updated so that it's correct if/when
> + * the vCPU does get initialized.
> + */
> + if (is_td_vcpu_created(to_tdx(vcpu))) {
> + /*
> + * No need to retry. TDX Resources needed for TDH.VP.FLUSH are,
> + * TDVPR as exclusive, TDR as shared, and TDCS as shared. This
> + * vp flush function is called when destructing vcpu/TD or vcpu
> + * migration. No other thread uses TDVPR in those cases.
> + */
> + err = tdh_vp_flush(to_tdx(vcpu)->tdvpr_pa);
> + if (unlikely(err && err != TDX_VCPU_NOT_ASSOCIATED)) {
> + /*
> + * This function is called in IPI context. Do not use
> + * printk to avoid console semaphore.
> + * The caller prints out the error message, instead.
> + */
> + if (err)
> + arg->err = err;
> + }
> + }
> +
> + tdx_disassociate_vp(vcpu);
> +}
> +
> +static void tdx_flush_vp_on_cpu(struct kvm_vcpu *vcpu)
> +{
> + struct tdx_flush_vp_arg arg = {
> + .vcpu = vcpu,
> + };
> + int cpu = vcpu->cpu;
> +
> + if (unlikely(cpu == -1))
> + return;
> +
> + smp_call_function_single(cpu, tdx_flush_vp, &arg, 1);
> + if (WARN_ON_ONCE(arg.err)) {
> + pr_err("cpu: %d ", cpu);
> + pr_tdx_error(TDH_VP_FLUSH, arg.err, NULL);
> + }
> +}
> +
> +void tdx_hardware_disable(void)
> +{
> + int cpu = raw_smp_processor_id();
> + struct list_head *tdvcpus = &per_cpu(associated_tdvcpus, cpu);
> + struct tdx_flush_vp_arg arg;
> + struct vcpu_tdx *tdx, *tmp;
> + unsigned long flags;
> +
> + lockdep_assert_preemption_disabled();
> +
> + local_irq_save(flags);
> + /* Safe variant needed as tdx_disassociate_vp() deletes the entry. */
> + list_for_each_entry_safe(tdx, tmp, tdvcpus, cpu_list) {
> + arg.vcpu = &tdx->vcpu;
> + tdx_flush_vp(&arg);
> + }
> + local_irq_restore(flags);
> +}
> +
> static void tdx_do_tdh_phymem_cache_wb(void *unused)
> {
> u64 err = 0;
> @@ -233,26 +353,31 @@ static void tdx_do_tdh_phymem_cache_wb(void *unused)
> pr_tdx_error(TDH_PHYMEM_CACHE_WB, err, NULL);
> }
>
> -void tdx_mmu_release_hkid(struct kvm *kvm)
> +static int __tdx_mmu_release_hkid(struct kvm *kvm)
> {
> bool packages_allocated, targets_allocated;
> struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
> cpumask_var_t packages, targets;
> + struct kvm_vcpu *vcpu;
> + unsigned long j;
> + int i, ret = 0;
> u64 err;
> - int i;
>
> if (!is_hkid_assigned(kvm_tdx))
> - return;
> + return 0;
>
> if (!is_td_created(kvm_tdx)) {
> tdx_hkid_free(kvm_tdx);
> - return;
> + return 0;
> }
>
> packages_allocated = zalloc_cpumask_var(&packages, GFP_KERNEL);
> targets_allocated = zalloc_cpumask_var(&targets, GFP_KERNEL);
> cpus_read_lock();
>
> + kvm_for_each_vcpu(j, vcpu, kvm)
> + tdx_flush_vp_on_cpu(vcpu);
> +
> /*
> * We can destroy multiple guest TDs simultaneously. Prevent
> * tdh_phymem_cache_wb from returning TDX_BUSY by serialization.
> @@ -270,6 +395,19 @@ void tdx_mmu_release_hkid(struct kvm *kvm)
> */
> write_lock(&kvm->mmu_lock);
>
> + err = tdh_mng_vpflushdone(kvm_tdx->tdr_pa);
> + if (err == TDX_FLUSHVP_NOT_DONE) {
> + ret = -EBUSY;
> + goto out;
> + }
> + if (WARN_ON_ONCE(err)) {
> + pr_tdx_error(TDH_MNG_VPFLUSHDONE, err, NULL);
> + pr_err("tdh_mng_vpflushdone() failed. HKID %d is leaked.\n",
> + kvm_tdx->hkid);
> + ret = -EIO;
> + goto out;
> + }
> +
> for_each_online_cpu(i) {
> if (packages_allocated &&
> cpumask_test_and_set_cpu(topology_physical_package_id(i),
> @@ -291,14 +429,24 @@ void tdx_mmu_release_hkid(struct kvm *kvm)
> pr_tdx_error(TDH_MNG_KEY_FREEID, err, NULL);
> pr_err("tdh_mng_key_freeid() failed. HKID %d is leaked.\n",
> kvm_tdx->hkid);
> + ret = -EIO;
> } else
> tdx_hkid_free(kvm_tdx);
>
> +out:
> write_unlock(&kvm->mmu_lock);
> mutex_unlock(&tdx_lock);
> cpus_read_unlock();
> free_cpumask_var(targets);
> free_cpumask_var(packages);
> +
> + return ret;
> +}
> +
> +void tdx_mmu_release_hkid(struct kvm *kvm)
> +{
> + while (__tdx_mmu_release_hkid(kvm) == -EBUSY)
> + ;
> }
>
> void tdx_vm_free(struct kvm *kvm)
> @@ -455,6 +603,26 @@ int tdx_vcpu_create(struct kvm_vcpu *vcpu)
> return 0;
> }
>
> +void tdx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> +{
> + struct vcpu_tdx *tdx = to_tdx(vcpu);
> +
> + if (vcpu->cpu == cpu)
> + return;
> +
> + tdx_flush_vp_on_cpu(vcpu);
> +
> + local_irq_disable();
> + /*
> + * Pairs with the smp_wmb() in tdx_disassociate_vp() to ensure
> + * vcpu->cpu is read before tdx->cpu_list.
> + */
> + smp_rmb();
> +
> + list_add(&tdx->cpu_list, &per_cpu(associated_tdvcpus, cpu));
> + local_irq_enable();
> +}
> +
> void tdx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
> {
> struct vcpu_tdx *tdx = to_tdx(vcpu);
> @@ -495,6 +663,16 @@ void tdx_vcpu_free(struct kvm_vcpu *vcpu)
> struct vcpu_tdx *tdx = to_tdx(vcpu);
> int i;
>
> + /*
> + * When destroying VM, kvm_unload_vcpu_mmu() calls vcpu_load() for every
> + * vcpu after they already disassociated from the per cpu list by
> + * tdx_mmu_release_hkid(). So we need to disassociate them again,
> + * otherwise the freed vcpu data will be accessed when do
> + * list_{del,add}() on associated_tdvcpus list later.
> + */
> + tdx_disassociate_vp_on_cpu(vcpu);
> + WARN_ON_ONCE(vcpu->cpu != -1);
> +
> /*
> * This methods can be called when vcpu allocation/initialization
> * failed. So it's possible that hkid, tdvpx and tdvpr are not assigned
> @@ -2030,6 +2208,10 @@ int __init tdx_hardware_setup(struct kvm_x86_ops *x86_ops)
> return -EINVAL;
> }
>
> + /* tdx_hardware_disable() uses associated_tdvcpus. */
> + for_each_possible_cpu(i)
> + INIT_LIST_HEAD(&per_cpu(associated_tdvcpus, i));
> +
> for (i = 0; i < ARRAY_SIZE(tdx_uret_msrs); i++) {
> /*
> * Here it checks if MSRs (tdx_uret_msrs) can be saved/restored
> diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
> index 0d8a98feb58e..7f8c78f06508 100644
> --- a/arch/x86/kvm/vmx/tdx.h
> +++ b/arch/x86/kvm/vmx/tdx.h
> @@ -73,6 +73,8 @@ struct vcpu_tdx {
> unsigned long *tdvpx_pa;
> bool td_vcpu_created;
>
> + struct list_head cpu_list;
> +
> union tdx_exit_reason exit_reason;
>
> bool initialized;
> diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
> index 9fd997c79c33..5853f29f0af3 100644
> --- a/arch/x86/kvm/vmx/x86_ops.h
> +++ b/arch/x86/kvm/vmx/x86_ops.h
> @@ -137,6 +137,7 @@ void vmx_setup_mce(struct kvm_vcpu *vcpu);
> #ifdef CONFIG_INTEL_TDX_HOST
> int __init tdx_hardware_setup(struct kvm_x86_ops *x86_ops);
> void tdx_hardware_unsetup(void);
> +void tdx_hardware_disable(void);
> bool tdx_is_vm_type_supported(unsigned long type);
> int tdx_offline_cpu(void);
>
> @@ -153,6 +154,7 @@ void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event);
> fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu);
> void tdx_prepare_switch_to_guest(struct kvm_vcpu *vcpu);
> void tdx_vcpu_put(struct kvm_vcpu *vcpu);
> +void tdx_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
> u8 tdx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
>
> int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp);
> @@ -171,6 +173,7 @@ void tdx_post_memory_mapping(struct kvm_vcpu *vcpu,
> #else
> static inline int tdx_hardware_setup(struct kvm_x86_ops *x86_ops) { return -EOPNOTSUPP; }
> static inline void tdx_hardware_unsetup(void) {}
> +static inline void tdx_hardware_disable(void) {}
> static inline bool tdx_is_vm_type_supported(unsigned long type) { return false; }
> static inline int tdx_offline_cpu(void) { return 0; }
>
> @@ -190,6 +193,7 @@ static inline void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) {}
> static inline fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu) { return EXIT_FASTPATH_NONE; }
> static inline void tdx_prepare_switch_to_guest(struct kvm_vcpu *vcpu) {}
> static inline void tdx_vcpu_put(struct kvm_vcpu *vcpu) {}
> +static inline void tdx_vcpu_load(struct kvm_vcpu *vcpu, int cpu) {}
> static inline u8 tdx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio) { return 0; }
>
> static inline int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp) { return -EOPNOTSUPP; }