Re: [PATCH v19 036/130] KVM: TDX: x86: Add ioctl to get TDX systemwide parameters

Huang, Kai
2024-03-21T22:26:59Z

On 26/02/2024 9:25 pm, Yamahata, Isaku wrote:
> From: Sean Christopherson <sean.j.christopherson@intel.com>
>
> Implement an ioctl to get system-wide parameters for TDX. Although the
> function is systemwide, vm scoped mem_enc ioctl works for userspace VMM
> like qemu and device scoped version is not define, re-use vm scoped
> mem_enc.

-EPARSE for the part starting from "and device scoped ...".

Grammar check please.

>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> v18:
> - drop the use of tdhsysinfo_struct and TDH.SYS.INFO, use TDH.SYS.RD().
> For that, dynamically allocate/free tdx_info.
> - drop the change of tools/arch/x86/include/uapi/asm/kvm.h.
>
> v14 -> v15:
> - ABI change: added supported_gpaw and reserved area.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> arch/x86/include/uapi/asm/kvm.h | 17 ++++++++++
> arch/x86/kvm/vmx/tdx.c | 56 +++++++++++++++++++++++++++++++++
> arch/x86/kvm/vmx/tdx.h | 3 ++
> 3 files changed, 76 insertions(+)
>
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index 9ea46d143bef..e28189c81691 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -604,4 +604,21 @@ struct kvm_tdx_cpuid_config {
> __u32 edx;
> };
>
> +/* supported_gpaw */
> +#define TDX_CAP_GPAW_48 (1 << 0)
> +#define TDX_CAP_GPAW_52 (1 << 1)
> +
> +struct kvm_tdx_capabilities {
> + __u64 attrs_fixed0;
> + __u64 attrs_fixed1;
> + __u64 xfam_fixed0;
> + __u64 xfam_fixed1;
> + __u32 supported_gpaw;
> + __u32 padding;
> + __u64 reserved[251];
> +
> + __u32 nr_cpuid_configs;
> + struct kvm_tdx_cpuid_config cpuid_configs[];
> +};
> +

I think you should use __DECLARE_FLEX_ARRAY().

It's already used in existing KVM UAPI header:

struct kvm_nested_state {
...
union {
__DECLARE_FLEX_ARRAY(struct kvm_vmx_nested_state_data,
vmx);
__DECLARE_FLEX_ARRAY(struct kvm_svm_nested_state_data,
svm);
} data;
}

> #endif /* _ASM_X86_KVM_H */
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 07a3f0f75f87..816ccdb4bc41 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -6,6 +6,7 @@
> #include "capabilities.h"
> #include "x86_ops.h"
> #include "x86.h"
> +#include "mmu.h"
> #include "tdx_arch.h"
> #include "tdx.h"
>
> @@ -55,6 +56,58 @@ struct tdx_info {
> /* Info about the TDX module. */
> static struct tdx_info *tdx_info;
>
> +static int tdx_get_capabilities(struct kvm_tdx_cmd *cmd)
> +{
> + struct kvm_tdx_capabilities __user *user_caps;
> + struct kvm_tdx_capabilities *caps = NULL;
> + int ret = 0;
> +
> + if (cmd->flags)
> + return -EINVAL;

Add a comment?

/* flags is reserved for future use */

> +
> + caps = kmalloc(sizeof(*caps), GFP_KERNEL);
> + if (!caps)
> + return -ENOMEM;
> +
> + user_caps = (void __user *)cmd->data;
> + if (copy_from_user(caps, user_caps, sizeof(*caps))) {
> + ret = -EFAULT;
> + goto out;
> + }
> +
> + if (caps->nr_cpuid_configs < tdx_info->num_cpuid_config) {
> + ret = -E2BIG;
> + goto out;
> + }
> +
> + *caps = (struct kvm_tdx_capabilities) {
> + .attrs_fixed0 = tdx_info->attributes_fixed0,
> + .attrs_fixed1 = tdx_info->attributes_fixed1,
> + .xfam_fixed0 = tdx_info->xfam_fixed0,
> + .xfam_fixed1 = tdx_info->xfam_fixed1,
> + .supported_gpaw = TDX_CAP_GPAW_48 |
> + ((kvm_get_shadow_phys_bits() >= 52 &&
> + cpu_has_vmx_ept_5levels()) ? TDX_CAP_GPAW_52 : 0),
> + .nr_cpuid_configs = tdx_info->num_cpuid_config,
> + .padding = 0,
> + };
> +
> + if (copy_to_user(user_caps, caps, sizeof(*caps))) {
> + ret = -EFAULT;
> + goto out;
> + }

Add an empty line.

> + if (copy_to_user(user_caps->cpuid_configs, &tdx_info->cpuid_configs,
> + tdx_info->num_cpuid_config *
> + sizeof(tdx_info->cpuid_configs[0]))) {
> + ret = -EFAULT;
> + }

I think the '{ }' is needed here.

> +
> +out:
> + /* kfree() accepts NULL. */
> + kfree(caps);
> + return ret;
> +}
> +
> int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
> {
> struct kvm_tdx_cmd tdx_cmd;
> @@ -68,6 +121,9 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
> mutex_lock(&kvm->lock);
>
> switch (tdx_cmd.id) {
> + case KVM_TDX_CAPABILITIES:
> + r = tdx_get_capabilities(&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 473013265bd8..22c0b57f69ca 100644
> --- a/arch/x86/kvm/vmx/tdx.h
> +++ b/arch/x86/kvm/vmx/tdx.h
> @@ -3,6 +3,9 @@
> #define __KVM_X86_TDX_H
>
> #ifdef CONFIG_INTEL_TDX_HOST
> +
> +#include "tdx_ops.h"
> +

It appears "tdx_ops.h" is used for making SEAMCALLs.

I don't see this patch uses any SEAMCALL so I am wondering whether this
chunk is needed here?

> struct kvm_tdx {
> struct kvm kvm;
> /* TDX specific members follow. */