Re: [PATCH 10/25] KVM: TDX: Initialize KVM supported capabilities when module setup

Xiaoyao Li
2024-09-05T13:36:23Z

On 9/4/2024 7:58 PM, Nikolay Borisov wrote:
>
>
> On 13.08.24 г. 1:48 ч., Rick Edgecombe wrote:
>> From: Xiaoyao Li <xiaoyao.li@intel.com>
>>
>> While TDX module reports a set of capabilities/features that it
>> supports, what KVM currently supports might be a subset of them.
>> E.g., DEBUG and PERFMON are supported by TDX module but currently not
>> supported by KVM.
>>
>> Introduce a new struct kvm_tdx_caps to store KVM's capabilities of TDX.
>> supported_attrs and suppported_xfam are validated against fixed0/1
>> values enumerated by TDX module. Configurable CPUID bits derive from TDX
>> module plus applying KVM's capabilities (KVM_GET_SUPPORTED_CPUID),
>> i.e., mask off the bits that are configurable in the view of TDX module
>> but not supported by KVM yet.
>>
>> KVM_TDX_CPUID_NO_SUBLEAF is the concept from TDX module, switch it to 0
>> and use KVM_CPUID_FLAG_SIGNIFCANT_INDEX, which are the concept of KVM.
>>
>> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
>> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
>> ---
>> uAPI breakout v1:
>>   - Change setup_kvm_tdx_caps() to use the exported 'struct tdx_sysinfo'
>>     pointer.
>>   - Change how to copy 'kvm_tdx_cpuid_config' since 'struct tdx_sysinfo'
>>     doesn't have 'kvm_tdx_cpuid_config'.
>>   - Updates for uAPI changes
>> ---
>>   arch/x86/include/uapi/asm/kvm.h |  2 -
>>   arch/x86/kvm/vmx/tdx.c          | 81 +++++++++++++++++++++++++++++++++
>>   2 files changed, 81 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/include/uapi/asm/kvm.h
>> b/arch/x86/include/uapi/asm/kvm.h
>> index 47caf508cca7..c9eb2e2f5559 100644
>> --- a/arch/x86/include/uapi/asm/kvm.h
>> +++ b/arch/x86/include/uapi/asm/kvm.h
>> @@ -952,8 +952,6 @@ struct kvm_tdx_cmd {
>>       __u64 hw_error;
>>   };
>> -#define KVM_TDX_CPUID_NO_SUBLEAF    ((__u32)-1)
>> -
>>   struct kvm_tdx_cpuid_config {
>>       __u32 leaf;
>>       __u32 sub_leaf;
>> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
>> index 90b44ebaf864..d89973e554f6 100644
>> --- a/arch/x86/kvm/vmx/tdx.c
>> +++ b/arch/x86/kvm/vmx/tdx.c
>> @@ -31,6 +31,19 @@ static void __used tdx_guest_keyid_free(int keyid)
>>       ida_free(&tdx_guest_keyid_pool, keyid);
>>   }
>> +#define KVM_TDX_CPUID_NO_SUBLEAF    ((__u32)-1)
>> +
>> +struct kvm_tdx_caps {
>> +    u64 supported_attrs;
>> +    u64 supported_xfam;
>> +
>> +    u16 num_cpuid_config;
>> +    /* This must the last member. */
>> +    DECLARE_FLEX_ARRAY(struct kvm_tdx_cpuid_config, cpuid_configs);
>> +};
>> +
>> +static struct kvm_tdx_caps *kvm_tdx_caps;
>> +
>>   static int tdx_get_capabilities(struct kvm_tdx_cmd *cmd)
>>   {
>>       const struct tdx_sysinfo_td_conf *td_conf = &tdx_sysinfo->td_conf;
>> @@ -131,6 +144,68 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
>>       return r;
>>   }
>> +#define KVM_SUPPORTED_TD_ATTRS (TDX_TD_ATTR_SEPT_VE_DISABLE)
>
> Why isn't TDX_TD_ATTR_DEBUG added as well?

Because so far KVM doesn't support all the features of a DEBUG TD for
userspace. e.g., KVM doesn't provide interface for userspace to
read/write private memory of DEBUG TD.

> <snip>