Re: [PATCH 14/25] KVM: TDX: initialize VM with TDX specific parameters

[Chenyi Qiang <chenyi.qiang@intel.com>]

On 8/13/2024 6:48 AM, Rick Edgecombe wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
> 
> After the crypto-protection key has been configured, TDX requires a
> VM-scope initialization as a step of creating the TDX guest.  This
> "per-VM" TDX initialization does the global configurations/features that
> the TDX guest can support, such as guest's CPUIDs (emulated by the TDX
> module), the maximum number of vcpus etc.
> 
> This "per-VM" TDX initialization must be done before any "vcpu-scope" TDX
> initialization.  To match this better, require the KVM_TDX_INIT_VM IOCTL()
> to be done before KVM creates any vcpus.
> 
> Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> ---
> uAPI breakout v1:
>  - Drop TDX_TD_XFAM_CET and use XFEATURE_MASK_CET_{USER, KERNEL}.
>  - Update for the wrapper functions for SEAMCALLs. (Sean)
>  - Move gfn_shared_mask settings into this patch due to MMU section move
>  - Fix bisectability issues in headers (Kai)
>  - Updates from seamcall overhaul (Kai)
>  - Allow userspace configure xfam directly
>  - Check if user sets non-configurable bits in CPUIDs
>  - Rename error->hw_error
>  - Move code change to tdx_module_setup() to __tdx_bringup() due to
>    initializing is done in post hardware_setup() now and
>    tdx_module_setup() is removed.  Remove the code to use API to read
>    global metadata but use exported 'struct tdx_sysinfo' pointer.
>  - Replace 'tdx_info->nr_tdcs_pages' with a wrapper
>    tdx_sysinfo_nr_tdcs_pages() because the 'struct tdx_sysinfo' doesn't
>    have nr_tdcs_pages directly.
>  - Replace tdx_info->max_vcpus_per_td with the new exported pointer in
>    tdx_vm_init().
>  - Decrease the reserved space for struct kvm_tdx_init_vm (Kai)
>  - Use sizeof_field() for struct kvm_tdx_init_vm cpuids (Tony)
>  - No need to init init_vm, it gets copied over in tdx_td_init() (Chao)
>  - Use kmalloc() instead of () kzalloc for init_vm in tdx_td_init() (Chao)
>  - Add more line breaks to tdx_td_init() to make code easier to read (Tony)
>  - Clarify patch description (Kai)
> 
> v19:
>  - Check NO_RBP_MOD of feature0 and set it
>  - Update the comment for PT and CET
> 
> v18:
>  - remove the change of tools/arch/x86/include/uapi/asm/kvm.h
>  - typo in comment. sha348 => sha384
>  - updated comment in setup_tdparams_xfam()
>  - fix setup_tdparams_xfam() to use init_vm instead of td_params
> 
> v16:
>  - Removed AMX check as the KVM upstream supports AMX.
>  - Added CET flag to guest supported xss
> ---
>  arch/x86/include/uapi/asm/kvm.h |  24 ++++
>  arch/x86/kvm/cpuid.c            |   7 +
>  arch/x86/kvm/cpuid.h            |   2 +
>  arch/x86/kvm/vmx/tdx.c          | 237 ++++++++++++++++++++++++++++++--
>  arch/x86/kvm/vmx/tdx.h          |   4 +
>  arch/x86/kvm/vmx/tdx_ops.h      |  12 ++
>  6 files changed, 276 insertions(+), 10 deletions(-)
> 

...

> +static int __tdx_td_init(struct kvm *kvm, struct td_params *td_params,
> +			 u64 *seamcall_err)
>  {
>  	struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
>  	cpumask_var_t packages;
> @@ -427,8 +547,9 @@ static int __tdx_td_init(struct kvm *kvm)
>  	unsigned long tdr_pa = 0;
>  	unsigned long va;
>  	int ret, i;
> -	u64 err;
> +	u64 err, rcx;
>  
> +	*seamcall_err = 0;
>  	ret = tdx_guest_keyid_alloc();
>  	if (ret < 0)
>  		return ret;
> @@ -543,10 +664,23 @@ static int __tdx_td_init(struct kvm *kvm)
>  		}
>  	}
>  
> -	/*
> -	 * Note, TDH_MNG_INIT cannot be invoked here.  TDH_MNG_INIT requires a dedicated
> -	 * ioctl() to define the configure CPUID values for the TD.
> -	 */
> +	err = tdh_mng_init(kvm_tdx, __pa(td_params), &rcx);
> +	if ((err & TDX_SEAMCALL_STATUS_MASK) == TDX_OPERAND_INVALID) {
> +		/*
> +		 * Because a user gives operands, don't warn.
> +		 * Return a hint to the user because it's sometimes hard for the
> +		 * user to figure out which operand is invalid.  SEAMCALL status
> +		 * code includes which operand caused invalid operand error.
> +		 */
> +		*seamcall_err = err;

I'm wondering if we could return or output more hint (i.e. the value of
rcx) in the case of invalid operand. For example, if seamcall returns
with INVALID_OPERAND_CPUID_CONFIG, rcx will contain the CPUID
leaf/sub-leaf info.

> +		ret = -EINVAL;
> +		goto teardown;
> +	} else if (WARN_ON_ONCE(err)) {
> +		pr_tdx_error_1(TDH_MNG_INIT, err, rcx);
> +		ret = -EIO;
> +		goto teardown;
> +	}
> +
>  	return 0;
>  
>  	/*
> @@ -592,6 +726,86 @@ static int __tdx_td_init(struct kvm *kvm)
>  	return ret;
>  }
>  
> +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;
> +	struct td_params *td_params = NULL;
> +	int ret;
> +
> +	BUILD_BUG_ON(sizeof(*init_vm) != 256 + sizeof_field(struct kvm_tdx_init_vm, cpuid));
> +	BUILD_BUG_ON(sizeof(struct td_params) != 1024);
> +
> +	if (is_hkid_assigned(kvm_tdx))
> +		return -EINVAL;
> +
> +	if (cmd->flags)
> +		return -EINVAL;
> +
> +	init_vm = kmalloc(sizeof(*init_vm) +
> +			  sizeof(init_vm->cpuid.entries[0]) * KVM_MAX_CPUID_ENTRIES,
> +			  GFP_KERNEL);
> +	if (!init_vm)
> +		return -ENOMEM;
> +
> +	if (copy_from_user(init_vm, u64_to_user_ptr(cmd->data), sizeof(*init_vm))) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	if (init_vm->cpuid.nent > KVM_MAX_CPUID_ENTRIES) {
> +		ret = -E2BIG;
> +		goto out;
> +	}
> +
> +	if (copy_from_user(init_vm->cpuid.entries,
> +			   u64_to_user_ptr(cmd->data) + sizeof(*init_vm),
> +			   flex_array_size(init_vm, cpuid.entries, init_vm->cpuid.nent))) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	if (memchr_inv(init_vm->reserved, 0, sizeof(init_vm->reserved))) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	if (init_vm->cpuid.padding) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	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;
> +
> +	ret = __tdx_td_init(kvm, td_params, &cmd->hw_error);
> +	if (ret)
> +		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;
> +
> +	if (td_params->exec_controls & TDX_EXEC_CONTROL_MAX_GPAW)
> +		kvm->arch.gfn_direct_bits = gpa_to_gfn(BIT_ULL(51));
> +	else
> +		kvm->arch.gfn_direct_bits = 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;
> @@ -613,6 +827,9 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
>  	case KVM_TDX_CAPABILITIES:
>  		r = tdx_get_capabilities(&tdx_cmd);
>  		break;
> +	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 268959d0f74f..8912cb6d5bc2 100644
> --- a/arch/x86/kvm/vmx/tdx.h
> +++ b/arch/x86/kvm/vmx/tdx.h
> @@ -16,7 +16,11 @@ struct kvm_tdx {
>  	unsigned long tdr_pa;
>  	unsigned long *tdcs_pa;
>  
> +	u64 attributes;
> +	u64 xfam;
>  	int hkid;
> +
> +	u64 tsc_offset;
>  };
>  
>  struct vcpu_tdx {
> diff --git a/arch/x86/kvm/vmx/tdx_ops.h b/arch/x86/kvm/vmx/tdx_ops.h
> index 3f64c871a3f2..0363d8544f42 100644
> --- a/arch/x86/kvm/vmx/tdx_ops.h
> +++ b/arch/x86/kvm/vmx/tdx_ops.h
> @@ -399,4 +399,16 @@ static inline u64 tdh_vp_wr(struct vcpu_tdx *tdx, u64 field, u64 val, u64 mask)
>  	return seamcall(TDH_VP_WR, &in);
>  }
>  
> +static __always_inline u64 td_tdcs_exec_read64(struct kvm_tdx *kvm_tdx, u32 field)
> +{
> +	u64 err, data;
> +
> +	err = tdh_mng_rd(kvm_tdx, TDCS_EXEC(field), &data);
> +	if (unlikely(err)) {
> +		pr_err("TDH_MNG_RD[EXEC.0x%x] failed: 0x%llx\n", field, err);
> +		return 0;
> +	}
> +	return data;
> +}
> +
>  #endif /* __KVM_X86_TDX_OPS_H */