Re: [PATCH v19 005/130] x86/virt/tdx: Export global metadata read infrastructure

[Binbin Wu]

On 2/26/2024 4:25 PM, isaku.yamahata@xxxxxxxxx wrote:
> From: Kai Huang <kai.huang@xxxxxxxxx>
>
> KVM will need to read a bunch of non-TDMR related metadata to create and
> run TDX guests.  Export the metadata read infrastructure for KVM to use.
>
> Specifically, export two helpers:
>
> 1) The helper which reads multiple metadata fields to a buffer of a
>     structure based on the "field ID -> structure member" mapping table.
>
> 2) The low level helper which just reads a given field ID.
>
> The two helpers cover cases when the user wants to cache a bunch of
> metadata fields to a certain structure and when the user just wants to
> query a specific metadata field on demand.  They are enough for KVM to
> use (and also should be enough for other potential users).
>
> Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx>
> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

Reviewed-by: Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx>

> ---
>   arch/x86/include/asm/tdx.h  | 22 ++++++++++++++++++++++
>   arch/x86/virt/vmx/tdx/tdx.c | 25 ++++++++-----------------
>   2 files changed, 30 insertions(+), 17 deletions(-)
>
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index eba178996d84..709b9483f9e4 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -116,6 +116,28 @@ static inline u64 sc_retry(sc_func_t func, u64 fn,
>   int tdx_cpu_enable(void);
>   int tdx_enable(void);
>   const char *tdx_dump_mce_info(struct mce *m);
> +
> +struct tdx_metadata_field_mapping {
> +	u64 field_id;
> +	int offset;
> +	int size;
> +};
> +
> +#define TD_SYSINFO_MAP(_field_id, _struct, _member)	\
> +	{ .field_id = MD_FIELD_ID_##_field_id,		\
> +	  .offset   = offsetof(_struct, _member),	\
> +	  .size     = sizeof(typeof(((_struct *)0)->_member)) }
> +
> +/*
> + * Read multiple global metadata fields to a buffer of a structure
> + * based on the "field ID -> structure member" mapping table.
> + */
> +int tdx_sys_metadata_read(const struct tdx_metadata_field_mapping *fields,
> +			  int nr_fields, void *stbuf);
> +
> +/* Read a single global metadata field */
> +int tdx_sys_metadata_field_read(u64 field_id, u64 *data);
> +
>   #else
>   static inline void tdx_init(void) { }
>   static inline int tdx_cpu_enable(void) { return -ENODEV; }
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index a19adc898df6..dc21310776ab 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -251,7 +251,7 @@ static int build_tdx_memlist(struct list_head *tmb_list)
>   	return ret;
>   }
>   
> -static int read_sys_metadata_field(u64 field_id, u64 *data)
> +int tdx_sys_metadata_field_read(u64 field_id, u64 *data)
>   {
>   	struct tdx_module_args args = {};
>   	int ret;
> @@ -270,6 +270,7 @@ static int read_sys_metadata_field(u64 field_id, u64 *data)
>   
>   	return 0;
>   }
> +EXPORT_SYMBOL_GPL(tdx_sys_metadata_field_read);
>   
>   /* Return the metadata field element size in bytes */
>   static int get_metadata_field_bytes(u64 field_id)
> @@ -295,7 +296,7 @@ static int stbuf_read_sys_metadata_field(u64 field_id,
>   	if (WARN_ON_ONCE(get_metadata_field_bytes(field_id) != bytes))
>   		return -EINVAL;
>   
> -	ret = read_sys_metadata_field(field_id, &tmp);
> +	ret = tdx_sys_metadata_field_read(field_id, &tmp);
>   	if (ret)
>   		return ret;
>   
> @@ -304,19 +305,8 @@ static int stbuf_read_sys_metadata_field(u64 field_id,
>   	return 0;
>   }
>   
> -struct field_mapping {
> -	u64 field_id;
> -	int offset;
> -	int size;
> -};
> -
> -#define TD_SYSINFO_MAP(_field_id, _struct, _member)	\
> -	{ .field_id = MD_FIELD_ID_##_field_id,		\
> -	  .offset   = offsetof(_struct, _member),	\
> -	  .size     = sizeof(typeof(((_struct *)0)->_member)) }
> -
> -static int read_sys_metadata(struct field_mapping *fields, int nr_fields,
> -			     void *stbuf)
> +int tdx_sys_metadata_read(const struct tdx_metadata_field_mapping *fields,
> +			  int nr_fields, void *stbuf)
>   {
>   	int i, ret;
>   
> @@ -331,6 +321,7 @@ static int read_sys_metadata(struct field_mapping *fields, int nr_fields,
>   
>   	return 0;
>   }
> +EXPORT_SYMBOL_GPL(tdx_sys_metadata_read);
>   
>   #define TD_SYSINFO_MAP_TDMR_INFO(_field_id, _member)	\
>   	TD_SYSINFO_MAP(_field_id, struct tdx_tdmr_sysinfo, _member)
> @@ -338,7 +329,7 @@ static int read_sys_metadata(struct field_mapping *fields, int nr_fields,
>   static int get_tdx_tdmr_sysinfo(struct tdx_tdmr_sysinfo *tdmr_sysinfo)
>   {
>   	/* Map TD_SYSINFO fields into 'struct tdx_tdmr_sysinfo': */
> -	const struct field_mapping fields[] = {
> +	const struct tdx_metadata_field_mapping fields[] = {
>   		TD_SYSINFO_MAP_TDMR_INFO(MAX_TDMRS,		max_tdmrs),
>   		TD_SYSINFO_MAP_TDMR_INFO(MAX_RESERVED_PER_TDMR, max_reserved_per_tdmr),
>   		TD_SYSINFO_MAP_TDMR_INFO(PAMT_4K_ENTRY_SIZE,    pamt_entry_size[TDX_PS_4K]),
> @@ -347,7 +338,7 @@ static int get_tdx_tdmr_sysinfo(struct tdx_tdmr_sysinfo *tdmr_sysinfo)
>   	};
>   
>   	/* Populate 'tdmr_sysinfo' fields using the mapping structure above: */
> -	return read_sys_metadata(fields, ARRAY_SIZE(fields), tdmr_sysinfo);
> +	return tdx_sys_metadata_read(fields, ARRAY_SIZE(fields), tdmr_sysinfo);
>   }
>   
>   /* Calculate the actual TDMR size */