Re: [PATCH v11 08/20] x86/virt/tdx: Get information about TDX module and TDX-capable memory

[David Hildenbrand <david@redhat.com>]

On 04.06.23 16:27, Kai Huang wrote:
> Start to transit out the "multi-steps" to initialize the TDX module.
> 
> TDX provides increased levels of memory confidentiality and integrity.
> This requires special hardware support for features like memory
> encryption and storage of memory integrity checksums.  Not all memory
> satisfies these requirements.
> 
> As a result, TDX introduced the concept of a "Convertible Memory Region"
> (CMR).  During boot, the firmware builds a list of all of the memory
> ranges which can provide the TDX security guarantees.
> 
> CMRs tell the kernel which memory is TDX compatible.  The kernel takes
> CMRs (plus a little more metadata) and constructs "TD Memory Regions"
> (TDMRs).  TDMRs let the kernel grant TDX protections to some or all of
> the CMR areas.
> 
> The TDX module also reports necessary information to let the kernel
> build TDMRs and run TDX guests in structure 'tdsysinfo_struct'.  The
> list of CMRs, along with the TDX module information, is available to
> the kernel by querying the TDX module.
> 
> As a preparation to construct TDMRs, get the TDX module information and
> the list of CMRs.  Print out CMRs to help user to decode which memory
> regions are TDX convertible.
> 
> The 'tdsysinfo_struct' is fairly large (1024 bytes) and contains a lot
> of info about the TDX module.  Fully define the entire structure, but
> only use the fields necessary to build the TDMRs and pr_info() some
> basics about the module.  The rest of the fields will get used by KVM.
> 
> For now both 'tdsysinfo_struct' and CMRs are only used during the module
> initialization.  But because they are both relatively big, declare them
> inside the module initialization function but as static variables.
> 
> Signed-off-by: Kai Huang <kai.huang@intel.com>
> Reviewed-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---


[...]


> ---
>   arch/x86/virt/vmx/tdx/tdx.c | 67 +++++++++++++++++++++++++++++++++-
>   arch/x86/virt/vmx/tdx/tdx.h | 72 +++++++++++++++++++++++++++++++++++++
>   2 files changed, 138 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index bcf2b2d15a2e..9fde0f71dd8b 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -20,6 +20,7 @@
>   #include <asm/msr-index.h>
>   #include <asm/msr.h>
>   #include <asm/archrandom.h>
> +#include <asm/page.h>
>   #include <asm/tdx.h>
>   #include "tdx.h"
>   
> @@ -191,12 +192,76 @@ int tdx_cpu_enable(void)
>   }
>   EXPORT_SYMBOL_GPL(tdx_cpu_enable);
>   
> +static inline bool is_cmr_empty(struct cmr_info *cmr)
> +{
> +	return !cmr->size;
> +}
> +

Nit: maybe it's just me, but this function seems unnecessary.

If "!cmr->size" is not expressive, then I don't know why "is_cmr_empty" 
should be. Just inline that into the single user.

.. after all the single caller also uses/prints cmr->size ...

> +static void print_cmrs(struct cmr_info *cmr_array, int nr_cmrs)
> +{
> +	int i;
> +
> +	for (i = 0; i < nr_cmrs; i++) {
> +		struct cmr_info *cmr = &cmr_array[i];
> +
> +		/*
> +		 * The array of CMRs reported via TDH.SYS.INFO can
> +		 * contain tail empty CMRs.  Don't print them.
> +		 */
> +		if (is_cmr_empty(cmr))
> +			break;
> +
> +		pr_info("CMR: [0x%llx, 0x%llx)\n", cmr->base,
> +				cmr->base + cmr->size);
> +	}
> +}
> +
> +/*
> + * Get the TDX module information (TDSYSINFO_STRUCT) and the array of
> + * CMRs, and save them to @sysinfo and @cmr_array.  @sysinfo must have
> + * been padded to have enough room to save the TDSYSINFO_STRUCT.
> + */
> +static int tdx_get_sysinfo(struct tdsysinfo_struct *sysinfo,
> +			   struct cmr_info *cmr_array)
> +{
> +	struct tdx_module_output out;
> +	u64 sysinfo_pa, cmr_array_pa;
> +	int ret;
> +
> +	sysinfo_pa = __pa(sysinfo);
> +	cmr_array_pa = __pa(cmr_array);
> +	ret = seamcall(TDH_SYS_INFO, sysinfo_pa, TDSYSINFO_STRUCT_SIZE,
> +			cmr_array_pa, MAX_CMRS, NULL, &out);
> +	if (ret)
> +		return ret;
> +
> +	pr_info("TDX module: atributes 0x%x, vendor_id 0x%x, major_version %u, minor_version %u, build_date %u, build_num %u",


"attributes" ?

> +		sysinfo->attributes,	sysinfo->vendor_id,
> +		sysinfo->major_version, sysinfo->minor_version,
> +		sysinfo->build_date,	sysinfo->build_num);
> +
> +	/* R9 contains the actual entries written to the CMR array. */
> +	print_cmrs(cmr_array, out.r9);
> +
> +	return 0;
> +}
> +
>   static int init_tdx_module(void)
>   {
> +	static DECLARE_PADDED_STRUCT(tdsysinfo_struct, tdsysinfo,
> +			TDSYSINFO_STRUCT_SIZE, TDSYSINFO_STRUCT_ALIGNMENT);
> +	static struct cmr_info cmr_array[MAX_CMRS]
> +			__aligned(CMR_INFO_ARRAY_ALIGNMENT);
> +	struct tdsysinfo_struct *sysinfo = &PADDED_STRUCT(tdsysinfo);
> +	int ret;
> +
> +	ret = tdx_get_sysinfo(sysinfo, cmr_array);
> +	if (ret)
> +		return ret;
> +
>   	/*
>   	 * TODO:
>   	 *
> -	 *  - Get TDX module information and TDX-capable memory regions.
>   	 *  - Build the list of TDX-usable memory regions.
>   	 *  - Construct a list of "TD Memory Regions" (TDMRs) to cover
>   	 *    all TDX-usable memory regions.
> diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
> index 9fb46033c852..97f4d7e7f1a4 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.h
> +++ b/arch/x86/virt/vmx/tdx/tdx.h
> @@ -3,6 +3,8 @@
>   #define _X86_VIRT_TDX_H
>   
>   #include <linux/types.h>
> +#include <linux/stddef.h>
> +#include <linux/compiler_attributes.h>
>   
>   /*
>    * This file contains both macros and data structures defined by the TDX
> @@ -21,6 +23,76 @@
>    */
>   #define TDH_SYS_INIT		33
>   #define TDH_SYS_LP_INIT		35
> +#define TDH_SYS_INFO		32
> +
> +struct cmr_info {
> +	u64	base;
> +	u64	size;
> +} __packed;
> +
> +#define MAX_CMRS			32
> +#define CMR_INFO_ARRAY_ALIGNMENT	512
> +
> +struct cpuid_config {
> +	u32	leaf;
> +	u32	sub_leaf;
> +	u32	eax;
> +	u32	ebx;
> +	u32	ecx;
> +	u32	edx;
> +} __packed;
> +
> +#define DECLARE_PADDED_STRUCT(type, name, size, alignment)	\
> +	struct type##_padded {					\
> +		union {						\
> +			struct type name;			\
> +			u8 padding[size];			\
> +		};						\
> +	} name##_padded __aligned(alignment)
> +
> +#define PADDED_STRUCT(name)	(name##_padded.name)
> +
> +#define TDSYSINFO_STRUCT_SIZE		1024

So, it can never be larger than 1024 bytes? Not even with many cpuid 
configs?

> +#define TDSYSINFO_STRUCT_ALIGNMENT	1024
> +

-- 
Cheers,

David / dhildenb