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Date: Fri, 6 May 2022 21:54:31 +0800
From: Xiaoyao Li <xiaoyao.li@...el.com>
To: isaku.yamahata@...el.com, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
erdemaktas@...gle.com, Sean Christopherson <seanjc@...gle.com>,
Sagi Shahar <sagis@...gle.com>
Subject: Re: [RFC PATCH v6 025/104] KVM: TDX: initialize VM with TDX specific
parameters
On 5/6/2022 2:14 AM, isaku.yamahata@...el.com wrote:
> From: Xiaoyao Li <xiaoyao.li@...el.com>
>
> TDX requires additional parameters for TDX VM for confidential execution to
> protect its confidentiality of its memory contents and its CPU state from
> any other software, including VMM. When creating guest TD VM before
> creating vcpu, the number of vcpu, TSC frequency (that is same among
> vcpus. and it can't be changed.) CPUIDs which is emulated by the TDX
> module. It means guest can trust those CPUIDs. and sha384 values for
> measurement.
>
> Add new subcommand, KVM_TDX_INIT_VM, to pass parameters for TDX guest. It
> assigns encryption key to the TDX guest for memory encryption. TDX
> encrypts memory per-guest bases. It assigns device model passes per-VM
> parameters for the TDX guest. The maximum number of vcpus, tsc frequency
> (TDX guest has fised VM-wide TSC frequency. not per-vcpu. The TDX guest
> can not change it.), attributes (production or debug), available extended
> features (which is reflected into guest XCR0, IA32_XSS MSR), cpuids, sha384
> measurements, and etc.
>
> This subcommand is called before creating vcpu and KVM_SET_CPUID2, i.e.
> cpuids configurations aren't available yet. So CPUIDs configuration values
> needs to be passed in struct kvm_init_vm. It's device model responsibility
> to make this cpuid config for KVM_TDX_INIT_VM and KVM_SET_CPUID2.
>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
> arch/x86/include/asm/kvm_host.h | 2 +
> arch/x86/include/uapi/asm/kvm.h | 33 +++++
> arch/x86/kvm/vmx/tdx.c | 205 ++++++++++++++++++++++++++
> arch/x86/kvm/vmx/tdx.h | 23 +++
> tools/arch/x86/include/uapi/asm/kvm.h | 33 +++++
> 5 files changed, 296 insertions(+)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index e6f6f8c8619f..bc2038157f11 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1250,6 +1250,8 @@ struct kvm_arch {
> * the global KVM_MAX_VCPU_IDS may lead to significant memory waste.
> */
> u32 max_vcpu_ids;
> +
> + gfn_t gfn_shared_mask;
> };
>
> struct kvm_vm_stat {
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index ca85a070ac19..0f067fe7c186 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -532,6 +532,7 @@ struct kvm_pmu_event_filter {
> /* Trust Domain eXtension sub-ioctl() commands. */
> enum kvm_tdx_cmd_id {
> KVM_TDX_CAPABILITIES = 0,
> + KVM_TDX_INIT_VM,
>
> KVM_TDX_CMD_NR_MAX,
> };
> @@ -577,4 +578,36 @@ struct kvm_tdx_capabilities {
> struct kvm_tdx_cpuid_config cpuid_configs[0];
> };
>
> +struct kvm_tdx_init_vm {
> + __u64 attributes;
> + __u32 max_vcpus;
> + __u32 tsc_khz;
> + __u64 mrconfigid[6]; /* sha384 digest */
> + __u64 mrowner[6]; /* sha384 digest */
> + __u64 mrownerconfig[6]; /* sha348 digest */
> + union {
> + /*
> + * KVM_TDX_INIT_VM is called before vcpu creation, thus before
> + * KVM_SET_CPUID2. CPUID configurations needs to be passed.
> + *
> + * This configuration supersedes KVM_SET_CPUID{,2}.
> + * The user space VMM, e.g. qemu, should make them consistent
> + * with this values.
> + * sizeof(struct kvm_cpuid_entry2) * KVM_MAX_CPUID_ENTRIES(256)
> + * = 8KB.
> + */
> + struct {
> + struct kvm_cpuid2 cpuid;
> + /* 8KB with KVM_MAX_CPUID_ENTRIES. */
> + struct kvm_cpuid_entry2 entries[];
> + };
> + /*
> + * For future extensibility.
> + * The size(struct kvm_tdx_init_vm) = 16KB.
> + * This should be enough given sizeof(TD_PARAMS) = 1024
> + */
> + __u64 reserved[2028];
I don't think it's a good idea to put the CPUID configs at the end of
this structure and put it into a union.
1. The union makes the Array of Length zero entries[] pointless.
2. It wastes memory that when new field to be added in the future, it
has to be put after union instead of inside union.
> + };
> +};
> +
> #endif /* _ASM_X86_KVM_H */
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index a4be3ef313b2..095ca7952114 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -438,6 +438,208 @@ int tdx_dev_ioctl(void __user *argp)
> return 0;
> }
>
> +#define TDX_CPUID_NO_INDEX ((u32)-1)
why do you bother introduing it in this version? I think we can use 0
for those leaves without significant index as previous versions.
> +static const struct kvm_cpuid_entry2 *tdx_find_cpuid_entry(
> + const struct kvm_tdx_init_vm *init_vm, u32 function, u32 index)
> +{
> + int i;
> +
> + for (i = 0; i < init_vm->cpuid.nent; i++) {
> + const struct kvm_cpuid_entry2 *e = &init_vm->entries[i];
> +
> + if (e->function == function &&
> + (e->index == index ||
> + !(e->flags & KVM_CPUID_FLAG_SIGNIFCANT_INDEX)))
> + return e;
> + }
> + return NULL;
> +}
> +
> +static int setup_tdparams(struct kvm *kvm, struct td_params *td_params,
> + struct kvm_tdx_init_vm *init_vm)
> +{
> + const struct kvm_cpuid_entry2 *entry;
> + u64 guest_supported_xcr0;
> + u64 guest_supported_xss;
> + u32 guest_tsc_khz;
> + int max_pa;
> + int i;
> +
> + td_params->max_vcpus = init_vm->max_vcpus;
> +
> + td_params->attributes = init_vm->attributes;
> + if (td_params->attributes & TDX_TD_ATTRIBUTE_PERFMON) {
> + /*
> + * TODO: save/restore PMU related registers around TDENTER.
> + * Once it's done, remove this guard.
> + */
> + pr_warn("TD doesn't support perfmon yet. KVM needs to save/restore "
> + "host perf registers properly.\n");
> + return -EOPNOTSUPP;
> + }
> +
> + for (i = 0; i < tdx_caps.nr_cpuid_configs; i++) {
> + const struct tdx_cpuid_config *config = &tdx_caps.cpuid_configs[i];
> + const struct kvm_cpuid_entry2 *entry =
> + tdx_find_cpuid_entry(init_vm, config->leaf, config->sub_leaf);
> + struct tdx_cpuid_value *value = &td_params->cpuid_values[i];
why
if (!entry)
continue;
get lost in this version?
> + value->eax = entry->eax & config->eax;
> + value->ebx = entry->ebx & config->ebx;
> + value->ecx = entry->ecx & config->ecx;
> + value->edx = entry->edx & config->edx;
> + }
> +
> + max_pa = 36;
> + entry = tdx_find_cpuid_entry(init_vm, 0x80000008, TDX_CPUID_NO_INDEX);
> + if (entry)
> + max_pa = entry->eax & 0xff;
> +
> + td_params->eptp_controls = VMX_EPTP_MT_WB;
> + /*
> + * No CPU supports 4-level && max_pa > 48.
> + * "5-level paging and 5-level EPT" section 4.1 4-level EPT
> + * "4-level EPT is limited to translating 48-bit guest-physical
> + * addresses."
> + * cpu_has_vmx_ept_5levels() check is just in case.
> + */
> + if (cpu_has_vmx_ept_5levels() && max_pa > 48) {
> + td_params->eptp_controls |= VMX_EPTP_PWL_5;
> + td_params->exec_controls |= TDX_EXEC_CONTROL_MAX_GPAW;
> + } else {
> + td_params->eptp_controls |= VMX_EPTP_PWL_4;
> + }
> +
> + /* Setup td_params.xfam */
> + entry = tdx_find_cpuid_entry(init_vm, 0xd, 0);
> + if (entry)
> + guest_supported_xcr0 = (entry->eax | ((u64)entry->edx << 32));
> + else
> + guest_supported_xcr0 = 0;
> + guest_supported_xcr0 &= supported_xcr0;
> +
> + entry = tdx_find_cpuid_entry(init_vm, 0xd, 1);
> + if (entry)
> + guest_supported_xss = (entry->ecx | ((u64)entry->edx << 32));
> + else
> + guest_supported_xss = 0;
> + /* PT can be exposed to TD guest regardless of KVM's XSS support */
> + guest_supported_xss &= (supported_xss | XFEATURE_MASK_PT);
> +
> + td_params->xfam = guest_supported_xcr0 | guest_supported_xss;
> + if (td_params->xfam & XFEATURE_MASK_LBR) {
> + /*
> + * TODO: once KVM supports LBR(save/restore LBR related
> + * registers around TDENTER), remove this guard.
> + */
> + pr_warn("TD doesn't support LBR yet. KVM needs to save/restore "
> + "IA32_LBR_DEPTH properly.\n");
> + return -EOPNOTSUPP;
> + }
> +
> + if (td_params->xfam & XFEATURE_MASK_XTILE) {
> + /*
> + * TODO: once KVM supports AMX(save/restore AMX related
> + * registers around TDENTER), remove this guard.
> + */
> + pr_warn("TD doesn't support AMX yet. KVM needs to save/restore "
> + "IA32_XFD, IA32_XFD_ERR properly.\n");
> + return -EOPNOTSUPP;
> + }
> +
> + if (init_vm->tsc_khz) {
> + guest_tsc_khz = init_vm->tsc_khz;
> + kvm->arch.default_tsc_khz = guest_tsc_khz;
> + } else
> + guest_tsc_khz = kvm->arch.default_tsc_khz;
> + td_params->tsc_frequency = TDX_TSC_KHZ_TO_25MHZ(guest_tsc_khz);
> +
> +#define MEMCPY_SAME_SIZE(dst, src) \
> + do { \
> + BUILD_BUG_ON(sizeof(dst) != sizeof(src)); \
> + memcpy((dst), (src), sizeof(dst)); \
> + } while (0)
> +
> + MEMCPY_SAME_SIZE(td_params->mrconfigid, init_vm->mrconfigid);
> + MEMCPY_SAME_SIZE(td_params->mrowner, init_vm->mrowner);
> + MEMCPY_SAME_SIZE(td_params->mrownerconfig, init_vm->mrownerconfig);
> +
> + return 0;
> +}
> +
> +static int tdx_td_init(struct kvm *kvm, struct kvm_tdx_cmd *cmd)
> +{
> + struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
> + struct kvm_tdx_init_vm *init_vm = NULL;
> + struct td_params *td_params = NULL;
> + struct tdx_module_output out;
> + int ret;
> + u64 err;
> +
> + BUILD_BUG_ON(sizeof(*init_vm) != 16 * 1024);
> + BUILD_BUG_ON((sizeof(*init_vm) - offsetof(typeof(*init_vm), entries)) /
> + sizeof(init_vm->entries[0]) < KVM_MAX_CPUID_ENTRIES);
> + BUILD_BUG_ON(sizeof(struct td_params) != 1024);
> +
> + if (is_td_initialized(kvm))
> + return -EINVAL;
> +
> + if (cmd->flags)
> + return -EINVAL;
> +
> + init_vm = kzalloc(sizeof(*init_vm), GFP_KERNEL);
> + if (copy_from_user(init_vm, (void __user *)cmd->data, sizeof(*init_vm))) {
> + ret = -EFAULT;
> + goto out;
> + }
> +
> + if (init_vm->max_vcpus > KVM_MAX_VCPUS) {
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + if (tdx_caps.nr_cpuid_configs > KVM_MAX_CPUID_ENTRIES) {
> + /* tdx_caps.nr_cpuis_configs should be smaller. */
> + pr_warn("too large nr_cpuid_configs\n");
> + ret = -E2BIG;
> + goto out;
> + }
No need to validate tdx_caps.nr_cpuid_configs here. It should and
already has been validated when tdx_caps is setting up in tdx_module_setup()
> +
> + td_params = kzalloc(sizeof(struct td_params), GFP_KERNEL);
> + if (!td_params) {
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + ret = setup_tdparams(kvm, td_params, init_vm);
> + if (ret)
> + goto out;
> +
> + err = tdh_mng_init(kvm_tdx->tdr.pa, __pa(td_params), &out);
> + if (WARN_ON_ONCE(err)) {
> + pr_tdx_error(TDH_MNG_INIT, err, &out);
> + ret = -EIO;
> + goto out;
> + }
> +
> + kvm_tdx->tsc_offset = td_tdcs_exec_read64(kvm_tdx, TD_TDCS_EXEC_TSC_OFFSET);
> + kvm_tdx->attributes = td_params->attributes;
> + kvm_tdx->xfam = td_params->xfam;
> + kvm_tdx->tsc_khz = TDX_TSC_25MHZ_TO_KHZ(td_params->tsc_frequency);
> + kvm->max_vcpus = td_params->max_vcpus;
> +
> + if (td_params->exec_controls & TDX_EXEC_CONTROL_MAX_GPAW)
> + kvm->arch.gfn_shared_mask = gpa_to_gfn(BIT_ULL(51));
> + else
> + kvm->arch.gfn_shared_mask = gpa_to_gfn(BIT_ULL(47));
> +
> +out:
> + /* kfree() accepts NULL. */
> + kfree(init_vm);
> + kfree(td_params);
> + return ret;
> +}
> +
> int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
> {
> struct kvm_tdx_cmd tdx_cmd;
> @@ -451,6 +653,9 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
> mutex_lock(&kvm->lock);
>
> switch (tdx_cmd.id) {
> + case KVM_TDX_INIT_VM:
> + r = tdx_td_init(kvm, &tdx_cmd);
> + break;
> default:
> r = -EINVAL;
> goto out;
> diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
> index 8058b6b153f8..8a0793fcc3ab 100644
> --- a/arch/x86/kvm/vmx/tdx.h
> +++ b/arch/x86/kvm/vmx/tdx.h
> @@ -20,7 +20,12 @@ struct kvm_tdx {
> struct tdx_td_page tdr;
> struct tdx_td_page *tdcs;
>
> + u64 attributes;
> + u64 xfam;
> int hkid;
> +
> + u64 tsc_offset;
> + unsigned long tsc_khz;
> };
>
> struct vcpu_tdx {
> @@ -50,6 +55,11 @@ static inline struct vcpu_tdx *to_tdx(struct kvm_vcpu *vcpu)
> return container_of(vcpu, struct vcpu_tdx, vcpu);
> }
>
> +static inline bool is_td_initialized(struct kvm *kvm)
> +{
> + return !!kvm->max_vcpus;
> +}
> +
> static __always_inline void tdvps_vmcs_check(u32 field, u8 bits)
> {
> BUILD_BUG_ON_MSG(__builtin_constant_p(field) && (field) & 0x1,
> @@ -135,6 +145,19 @@ TDX_BUILD_TDVPS_ACCESSORS(64, VMCS, vmcs);
> TDX_BUILD_TDVPS_ACCESSORS(64, STATE_NON_ARCH, state_non_arch);
> TDX_BUILD_TDVPS_ACCESSORS(8, MANAGEMENT, management);
>
> +static __always_inline u64 td_tdcs_exec_read64(struct kvm_tdx *kvm_tdx, u32 field)
> +{
> + struct tdx_module_output out;
> + u64 err;
> +
> + err = tdh_mng_rd(kvm_tdx->tdr.pa, TDCS_EXEC(field), &out);
> + if (unlikely(err)) {
> + pr_err("TDH_MNG_RD[EXEC.0x%x] failed: 0x%llx\n", field, err);
> + return 0;
> + }
> + return out.r8;
> +}
> +
> #else
> static inline int tdx_module_setup(void) { return -ENODEV; };
>
> diff --git a/tools/arch/x86/include/uapi/asm/kvm.h b/tools/arch/x86/include/uapi/asm/kvm.h
> index a9ea3573be1b..779dfd683d66 100644
> --- a/tools/arch/x86/include/uapi/asm/kvm.h
> +++ b/tools/arch/x86/include/uapi/asm/kvm.h
> @@ -531,6 +531,7 @@ struct kvm_pmu_event_filter {
> /* Trust Domain eXtension sub-ioctl() commands. */
> enum kvm_tdx_cmd_id {
> KVM_TDX_CAPABILITIES = 0,
> + KVM_TDX_INIT_VM,
>
> KVM_TDX_CMD_NR_MAX,
> };
> @@ -576,4 +577,36 @@ struct kvm_tdx_capabilities {
> struct kvm_tdx_cpuid_config cpuid_configs[0];
> };
>
> +struct kvm_tdx_init_vm {
> + __u64 attributes;
> + __u32 max_vcpus;
> + __u32 tsc_khz;
> + __u64 mrconfigid[6]; /* sha384 digest */
> + __u64 mrowner[6]; /* sha384 digest */
> + __u64 mrownerconfig[6]; /* sha348 digest */
> + union {
> + /*
> + * KVM_TDX_INIT_VM is called before vcpu creation, thus before
> + * KVM_SET_CPUID2. CPUID configurations needs to be passed.
> + *
> + * This configuration supersedes KVM_SET_CPUID{,2}.
> + * The user space VMM, e.g. qemu, should make them consistent
> + * with this values.
> + * sizeof(struct kvm_cpuid_entry2) * KVM_MAX_CPUID_ENTRIES(256)
> + * = 8KB.
> + */
> + struct {
> + struct kvm_cpuid2 cpuid;
> + /* 8KB with KVM_MAX_CPUID_ENTRIES. */
> + struct kvm_cpuid_entry2 entries[];
> + };
> + /*
> + * For future extensibility.
> + * The size(struct kvm_tdx_init_vm) = 16KB.
> + * This should be enough given sizeof(TD_PARAMS) = 1024
> + */
> + __u64 reserved[2028];
> + };
> +};
> +
> #endif /* _ASM_X86_KVM_H */
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