Re: [PATCH v8 020/103] KVM: TDX: create/destroy VM structure
From: Erdem Aktas
Date: Tue Aug 23 2022 - 20:53:19 EST
On Sun, Aug 7, 2022 at 3:03 PM <isaku.yamahata@xxxxxxxxx> wrote:
>
> From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
>
> As the first step to create TDX guest, create/destroy VM struct. Assign
> TDX private Host Key ID (HKID) to the TDX guest for memory encryption and
> allocate extra pages for the TDX guest. On destruction, free allocated
> pages, and HKID.
>
> Before tearing down private page tables, TDX requires some resources of the
> guest TD to be destroyed (i.e. keyID must have been reclaimed, etc). Add
> flush_shadow_all_private callback before tearing down private page tables
> for it.
>
> Add a second kvm_x86_ops hook in kvm_arch_destroy_vm() to support TDX's
> destruction path, which needs to first put the VM into a teardown state,
> then free per-vCPU resources, and finally free per-VM resources.
>
> Co-developed-by: Kai Huang <kai.huang@xxxxxxxxx>
> Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> ---
> arch/x86/include/asm/kvm-x86-ops.h | 2 +
> arch/x86/include/asm/kvm_host.h | 2 +
> arch/x86/kvm/vmx/main.c | 34 ++-
> arch/x86/kvm/vmx/tdx.c | 364 +++++++++++++++++++++++++++++
> arch/x86/kvm/vmx/tdx.h | 2 +
> arch/x86/kvm/vmx/x86_ops.h | 11 +
> arch/x86/kvm/x86.c | 8 +
> 7 files changed, 420 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
> index 3857bff6949c..968e5ba1e4e6 100644
> --- a/arch/x86/include/asm/kvm-x86-ops.h
> +++ b/arch/x86/include/asm/kvm-x86-ops.h
> @@ -21,7 +21,9 @@ KVM_X86_OP(has_emulated_msr)
> KVM_X86_OP(vcpu_after_set_cpuid)
> KVM_X86_OP(is_vm_type_supported)
> KVM_X86_OP(vm_init)
> +KVM_X86_OP_OPTIONAL(flush_shadow_all_private)
> KVM_X86_OP_OPTIONAL(vm_destroy)
> +KVM_X86_OP_OPTIONAL(vm_free)
> KVM_X86_OP_OPTIONAL_RET0(vcpu_precreate)
> KVM_X86_OP(vcpu_create)
> KVM_X86_OP(vcpu_free)
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index a371f806f6d8..7a8a3d76346e 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1458,7 +1458,9 @@ struct kvm_x86_ops {
> bool (*is_vm_type_supported)(unsigned long vm_type);
> unsigned int vm_size;
> int (*vm_init)(struct kvm *kvm);
> + void (*flush_shadow_all_private)(struct kvm *kvm);
> void (*vm_destroy)(struct kvm *kvm);
> + void (*vm_free)(struct kvm *kvm);
>
> /* Create, but do not attach this VCPU */
> int (*vcpu_precreate)(struct kvm *kvm);
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index 47bfa94e538e..6a93b19a8b06 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -39,18 +39,44 @@ static int __init vt_post_hardware_enable_setup(void)
> return 0;
> }
>
> +static void vt_hardware_unsetup(void)
> +{
> + tdx_hardware_unsetup();
> + vmx_hardware_unsetup();
> +}
> +
> static int vt_vm_init(struct kvm *kvm)
> {
> if (is_td(kvm))
> - return -EOPNOTSUPP; /* Not ready to create guest TD yet. */
> + return tdx_vm_init(kvm);
>
> return vmx_vm_init(kvm);
> }
>
> +static void vt_flush_shadow_all_private(struct kvm *kvm)
> +{
> + if (is_td(kvm))
> + return tdx_mmu_release_hkid(kvm);
> +}
> +
> +static void vt_vm_destroy(struct kvm *kvm)
> +{
> + if (is_td(kvm))
> + return;
> +
> + vmx_vm_destroy(kvm);
> +}
> +
> +static void vt_vm_free(struct kvm *kvm)
> +{
> + if (is_td(kvm))
> + return tdx_vm_free(kvm);
> +}
> +
> struct kvm_x86_ops vt_x86_ops __initdata = {
> .name = "kvm_intel",
>
> - .hardware_unsetup = vmx_hardware_unsetup,
> + .hardware_unsetup = vt_hardware_unsetup,
> .check_processor_compatibility = vmx_check_processor_compatibility,
>
> .hardware_enable = vmx_hardware_enable,
> @@ -60,7 +86,9 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
> .is_vm_type_supported = vt_is_vm_type_supported,
> .vm_size = sizeof(struct kvm_vmx),
> .vm_init = vt_vm_init,
> - .vm_destroy = vmx_vm_destroy,
> + .flush_shadow_all_private = vt_flush_shadow_all_private,
> + .vm_destroy = vt_vm_destroy,
> + .vm_free = vt_vm_free,
>
> .vcpu_precreate = vmx_vcpu_precreate,
> .vcpu_create = vmx_vcpu_create,
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 386bb2e86b77..4e6c3bc99777 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -31,6 +31,353 @@ struct tdx_capabilities {
> /* Capabilities of KVM + the TDX module. */
> static struct tdx_capabilities tdx_caps;
>
> +/*
> + * Some TDX SEAMCALLs (TDH.MNG.CREATE, TDH.PHYMEM.CACHE.WB,
> + * TDH.MNG.KEY.RECLAIMID, TDH.MNG.KEY.FREEID etc) tries to acquire a global lock
> + * internally in TDX module. If failed, TDX_OPERAND_BUSY is returned without
> + * spinning or waiting due to a constraint on execution time. It's caller's
> + * responsibility to avoid race (or retry on TDX_OPERAND_BUSY). Use this mutex
> + * to avoid race in TDX module because the kernel knows better about scheduling.
> + */
> +static DEFINE_MUTEX(tdx_lock);
> +static struct mutex *tdx_mng_key_config_lock;
> +
> +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);
> +}
> +
> +static inline bool is_td_created(struct kvm_tdx *kvm_tdx)
> +{
> + return kvm_tdx->tdr.added;
> +}
> +
> +static inline void tdx_hkid_free(struct kvm_tdx *kvm_tdx)
> +{
> + tdx_keyid_free(kvm_tdx->hkid);
> + kvm_tdx->hkid = -1;
> +}
> +
> +static inline bool is_hkid_assigned(struct kvm_tdx *kvm_tdx)
> +{
> + return kvm_tdx->hkid > 0;
> +}
> +
> +static void tdx_clear_page(unsigned long page)
> +{
> + const void *zero_page = (const void *) __va(page_to_phys(ZERO_PAGE(0)));
> + unsigned long i;
> +
> + /*
> + * Zeroing the page is only necessary for systems with MKTME-i:
> + * when re-assign one page from old keyid to a new keyid, MOVDIR64B is
> + * required to clear/write the page with new keyid to prevent integrity
> + * error when read on the page with new keyid.
> + */
Are we saying that we do not need to use MOVDIR64B to clear pages with Li?
> + if (!static_cpu_has(X86_FEATURE_MOVDIR64B))
> + return;
> +
> + for (i = 0; i < 4096; i += 64)
> + /* MOVDIR64B [rdx], es:rdi */
> + asm (".byte 0x66, 0x0f, 0x38, 0xf8, 0x3a"
> + : : "d" (zero_page), "D" (page + i) : "memory");
> +}
According to the Software Developer Manual, mfence is required for a
strong ordering on stores. Should we not use mfence here?
> +
> +static int tdx_reclaim_page(unsigned long va, hpa_t pa, bool do_wb, u16 hkid)
> +{
> + struct tdx_module_output out;
> + u64 err;
> +
> + err = tdh_phymem_page_reclaim(pa, &out);
> + if (WARN_ON_ONCE(err)) {
> + pr_tdx_error(TDH_PHYMEM_PAGE_RECLAIM, err, &out);
> + return -EIO;
> + }
> +
> + if (do_wb) {
> + err = tdh_phymem_page_wbinvd(set_hkid_to_hpa(pa, hkid));
> + if (WARN_ON_ONCE(err)) {
> + pr_tdx_error(TDH_PHYMEM_PAGE_WBINVD, err, NULL);
> + return -EIO;
> + }
> + }
> +
> + tdx_clear_page(va);
> + return 0;
> +}
> +
> +static int tdx_alloc_td_page(struct tdx_td_page *page)
> +{
> + page->va = __get_free_page(GFP_KERNEL_ACCOUNT);
> + if (!page->va)
> + return -ENOMEM;
> +
> + page->pa = __pa(page->va);
> + return 0;
> +}
> +
> +static void tdx_mark_td_page_added(struct tdx_td_page *page)
> +{
> + WARN_ON_ONCE(page->added);
> + page->added = true;
> +}
> +
> +static void tdx_reclaim_td_page(struct tdx_td_page *page)
> +{
> + if (page->added) {
> + /*
> + * TDCX are being reclaimed. TDX module maps TDCX with HKID
> + * assigned to the TD. Here the cache associated to the TD
> + * was already flushed by TDH.PHYMEM.CACHE.WB before here, So
> + * cache doesn't need to be flushed again.
> + */
> + if (tdx_reclaim_page(page->va, page->pa, false, 0))
> + return;
> +
> + page->added = false;
> + }
> + free_page(page->va);
> +}
> +
> +static int tdx_do_tdh_phymem_cache_wb(void *param)
> +{
> + u64 err = 0;
> +
> + do {
> + err = tdh_phymem_cache_wb(!!err);
> + } while (err == TDX_INTERRUPTED_RESUMABLE);
> +
> + /* Other thread may have done for us. */
> + if (err == TDX_NO_HKID_READY_TO_WBCACHE)
> + err = TDX_SUCCESS;
> + if (WARN_ON_ONCE(err)) {
> + pr_tdx_error(TDH_PHYMEM_CACHE_WB, err, NULL);
> + return -EIO;
> + }
> +
> + return 0;
> +}
> +
> +void tdx_mmu_release_hkid(struct kvm *kvm)
> +{
> + struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
> + cpumask_var_t packages;
> + bool cpumask_allocated;
> + u64 err;
> + int ret;
> + int i;
> +
> + if (!is_hkid_assigned(kvm_tdx))
> + return;
> +
> + if (!is_td_created(kvm_tdx))
> + goto free_hkid;
> +
> + cpumask_allocated = zalloc_cpumask_var(&packages, GFP_KERNEL);
> + cpus_read_lock();
> + for_each_online_cpu(i) {
> + if (cpumask_allocated &&
> + cpumask_test_and_set_cpu(topology_physical_package_id(i),
> + packages))
> + continue;
> +
> + /*
> + * We can destroy multiple the guest TDs simultaneously.
> + * Prevent tdh_phymem_cache_wb from returning TDX_BUSY by
> + * serialization.
> + */
> + mutex_lock(&tdx_lock);
> + ret = smp_call_on_cpu(i, tdx_do_tdh_phymem_cache_wb, NULL, 1);
> + mutex_unlock(&tdx_lock);
> + if (ret)
> + break;
> + }
> + cpus_read_unlock();
> + free_cpumask_var(packages);
> +
> + mutex_lock(&tdx_lock);
> + err = tdh_mng_key_freeid(kvm_tdx->tdr.pa);
> + mutex_unlock(&tdx_lock);
> + if (WARN_ON_ONCE(err)) {
> + pr_tdx_error(TDH_MNG_KEY_FREEID, err, NULL);
> + pr_err("tdh_mng_key_freeid failed. HKID %d is leaked.\n",
> + kvm_tdx->hkid);
> + return;
> + }
> +
> +free_hkid:
> + tdx_hkid_free(kvm_tdx);
> +}
> +
> +void tdx_vm_free(struct kvm *kvm)
> +{
> + struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
> + int i;
> +
> + /* Can't reclaim or free TD pages if teardown failed. */
> + if (is_hkid_assigned(kvm_tdx))
> + return;
> +
> + for (i = 0; i < tdx_caps.tdcs_nr_pages; i++)
> + tdx_reclaim_td_page(&kvm_tdx->tdcs[i]);
> + kfree(kvm_tdx->tdcs);
> +
> + /*
> + * TDX module maps TDR with TDX global HKID. TDX module may access TDR
> + * while operating on TD (Especially reclaiming TDCS). Cache flush with
> + * TDX global HKID is needed.
> + */
> + if (kvm_tdx->tdr.added &&
> + tdx_reclaim_page(kvm_tdx->tdr.va, kvm_tdx->tdr.pa, true,
> + tdx_global_keyid))
> + return;
> +
> + free_page(kvm_tdx->tdr.va);
> +}
> +
> +static int tdx_do_tdh_mng_key_config(void *param)
> +{
> + hpa_t *tdr_p = param;
> + u64 err;
> +
> + do {
> + err = tdh_mng_key_config(*tdr_p);
> +
> + /*
> + * If it failed to generate a random key, retry it because this
> + * is typically caused by an entropy error of the CPU's random
> + * number generator.
> + */
> + } while (err == TDX_KEY_GENERATION_FAILED);
> +
> + if (WARN_ON_ONCE(err)) {
> + pr_tdx_error(TDH_MNG_KEY_CONFIG, err, NULL);
> + return -EIO;
> + }
> +
> + return 0;
> +}
> +
> +int tdx_vm_init(struct kvm *kvm)
> +{
> + struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
> + cpumask_var_t packages;
> + int ret, i;
> + u64 err;
> +
> + /* vCPUs can't be created until after KVM_TDX_INIT_VM. */
> + kvm->max_vcpus = 0;
> +
> + kvm_tdx->hkid = tdx_keyid_alloc();
> + if (kvm_tdx->hkid < 0)
> + return -EBUSY;
> +
> + ret = tdx_alloc_td_page(&kvm_tdx->tdr);
> + if (ret)
> + goto free_hkid;
> +
> + kvm_tdx->tdcs = kcalloc(tdx_caps.tdcs_nr_pages, sizeof(*kvm_tdx->tdcs),
> + GFP_KERNEL_ACCOUNT);
> + if (!kvm_tdx->tdcs)
> + goto free_tdr;
> + for (i = 0; i < tdx_caps.tdcs_nr_pages; i++) {
> + ret = tdx_alloc_td_page(&kvm_tdx->tdcs[i]);
> + if (ret)
> + goto free_tdcs;
> + }
> +
> + /*
> + * Acquire global lock to avoid TDX_OPERAND_BUSY:
> + * TDH.MNG.CREATE and other APIs try to lock the global Key Owner
> + * Table (KOT) to track the assigned TDX private HKID. It doesn't spin
> + * to acquire the lock, returns TDX_OPERAND_BUSY instead, and let the
> + * caller to handle the contention. This is because of time limitation
> + * usable inside the TDX module and OS/VMM knows better about process
> + * scheduling.
> + *
> + * APIs to acquire the lock of KOT:
> + * TDH.MNG.CREATE, TDH.MNG.KEY.FREEID, TDH.MNG.VPFLUSHDONE, and
> + * TDH.PHYMEM.CACHE.WB.
> + */
> + mutex_lock(&tdx_lock);
> + err = tdh_mng_create(kvm_tdx->tdr.pa, kvm_tdx->hkid);
> + mutex_unlock(&tdx_lock);
> + if (WARN_ON_ONCE(err)) {
> + pr_tdx_error(TDH_MNG_CREATE, err, NULL);
> + ret = -EIO;
> + goto free_tdcs;
> + }
> + tdx_mark_td_page_added(&kvm_tdx->tdr);
> +
> + if (!zalloc_cpumask_var(&packages, GFP_KERNEL)) {
> + ret = -ENOMEM;
> + goto free_tdcs;
> + }
> + cpus_read_lock();
> + for_each_online_cpu(i) {
> + int pkg = topology_physical_package_id(i);
> +
> + if (cpumask_test_and_set_cpu(pkg, packages))
> + continue;
> +
> + /*
> + * Program the memory controller in the package with an
> + * encryption key associated to a TDX private host key id
> + * assigned to this TDR. Concurrent operations on same memory
> + * controller results in TDX_OPERAND_BUSY. Avoid this race by
> + * mutex.
> + */
> + mutex_lock(&tdx_mng_key_config_lock[pkg]);
> + ret = smp_call_on_cpu(i, tdx_do_tdh_mng_key_config,
> + &kvm_tdx->tdr.pa, true);
> + mutex_unlock(&tdx_mng_key_config_lock[pkg]);
> + if (ret)
> + break;
> + }
> + cpus_read_unlock();
> + free_cpumask_var(packages);
> + if (ret)
> + goto teardown;
> +
> + for (i = 0; i < tdx_caps.tdcs_nr_pages; i++) {
> + err = tdh_mng_addcx(kvm_tdx->tdr.pa, kvm_tdx->tdcs[i].pa);
> + if (WARN_ON_ONCE(err)) {
> + pr_tdx_error(TDH_MNG_ADDCX, err, NULL);
> + ret = -EIO;
> + goto teardown;
> + }
> + tdx_mark_td_page_added(&kvm_tdx->tdcs[i]);
> + }
> +
> + /*
> + * Note, TDH_MNG_INIT cannot be invoked here. TDH_MNG_INIT requires a dedicated
> + * ioctl() to define the configure CPUID values for the TD.
> + */
> + return 0;
> +
> + /*
> + * The sequence for freeing resources from a partially initialized TD
> + * varies based on where in the initialization flow failure occurred.
> + * Simply use the full teardown and destroy, which naturally play nice
> + * with partial initialization.
> + */
> +teardown:
> + tdx_mmu_release_hkid(kvm);
> + tdx_vm_free(kvm);
> + return ret;
> +
> +free_tdcs:
> + /* @i points at the TDCS page that failed allocation. */
> + for (--i; i >= 0; i--)
> + free_page(kvm_tdx->tdcs[i].va);
> + kfree(kvm_tdx->tdcs);
> +free_tdr:
> + free_page(kvm_tdx->tdr.va);
> +free_hkid:
> + tdx_hkid_free(kvm_tdx);
> + return ret;
> +}
> +
> int __init tdx_module_setup(void)
> {
> const struct tdsysinfo_struct *tdsysinfo;
> @@ -78,6 +425,9 @@ bool tdx_is_vm_type_supported(unsigned long type)
>
> int __init tdx_hardware_setup(struct kvm_x86_ops *x86_ops)
> {
> + int max_pkgs;
> + int i;
> +
> if (!enable_ept) {
> pr_warn("Cannot enable TDX with EPT disabled\n");
> return -EINVAL;
> @@ -88,8 +438,22 @@ int __init tdx_hardware_setup(struct kvm_x86_ops *x86_ops)
> return -ENODEV;
> }
>
> + max_pkgs = topology_max_packages();
> + tdx_mng_key_config_lock = kcalloc(max_pkgs, sizeof(*tdx_mng_key_config_lock),
> + GFP_KERNEL);
> + if (!tdx_mng_key_config_lock)
> + return -ENOMEM;
> + for (i = 0; i < max_pkgs; i++)
> + mutex_init(&tdx_mng_key_config_lock[i]);
> +
> pr_info("kvm: TDX is supported. x86 phys bits %d\n",
> boot_cpu_data.x86_phys_bits);
>
> return 0;
> }
> +
> +void tdx_hardware_unsetup(void)
> +{
> + /* kfree accepts NULL. */
> + kfree(tdx_mng_key_config_lock);
> +}
> diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
> index f50d37f3fc9c..8058b6b153f8 100644
> --- a/arch/x86/kvm/vmx/tdx.h
> +++ b/arch/x86/kvm/vmx/tdx.h
> @@ -19,6 +19,8 @@ struct kvm_tdx {
>
> struct tdx_td_page tdr;
> struct tdx_td_page *tdcs;
> +
> + int hkid;
> };
>
> struct vcpu_tdx {
> diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
> index 3f194ed53f07..cf616f9f0a07 100644
> --- a/arch/x86/kvm/vmx/x86_ops.h
> +++ b/arch/x86/kvm/vmx/x86_ops.h
> @@ -131,9 +131,20 @@ void vmx_setup_mce(struct kvm_vcpu *vcpu);
> #ifdef CONFIG_INTEL_TDX_HOST
> int __init tdx_hardware_setup(struct kvm_x86_ops *x86_ops);
> bool tdx_is_vm_type_supported(unsigned long type);
> +void tdx_hardware_unsetup(void);
> +
> +int tdx_vm_init(struct kvm *kvm);
> +void tdx_mmu_release_hkid(struct kvm *kvm);
> +void tdx_vm_free(struct kvm *kvm);
> #else
> static inline int tdx_hardware_setup(struct kvm_x86_ops *x86_ops) { return 0; }
> static inline bool tdx_is_vm_type_supported(unsigned long type) { return false; }
> +static inline void tdx_hardware_unsetup(void) {}
> +
> +static inline int tdx_vm_init(struct kvm *kvm) { return -EOPNOTSUPP; }
> +static inline void tdx_mmu_release_hkid(struct kvm *kvm) {}
> +static inline void tdx_flush_shadow_all_private(struct kvm *kvm) {}
> +static inline void tdx_vm_free(struct kvm *kvm) {}
> #endif
>
> #endif /* __KVM_X86_VMX_X86_OPS_H */
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 4bba34c8cf1a..0b8152d14052 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -12248,6 +12248,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
> kvm_page_track_cleanup(kvm);
> kvm_xen_destroy_vm(kvm);
> kvm_hv_destroy_vm(kvm);
> + static_call_cond(kvm_x86_vm_free)(kvm);
> }
>
> static void memslot_rmap_free(struct kvm_memory_slot *slot)
> @@ -12512,6 +12513,13 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
>
> void kvm_arch_flush_shadow_all(struct kvm *kvm)
> {
> + /*
> + * kvm_mmu_zap_all() zaps both private and shared page tables. Before
> + * tearing down private page tables, TDX requires some TD resources to
> + * be destroyed (i.e. keyID must have been reclaimed, etc). Invoke
> + * kvm_x86_flush_shadow_all_private() for this.
> + */
> + static_call_cond(kvm_x86_flush_shadow_all_private)(kvm);
> kvm_mmu_zap_all(kvm);
> }
>
> --
> 2.25.1
>