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