Re: [PATCH v19 004/130] x86/virt/tdx: Support global metadata read for all element sizes

Juergen Gross
2024-02-26T14:32:53Z

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On 26.02.24 09:25, isaku.yamahata@intel.com wrote:
> From: Kai Huang <kai.huang@intel.com>
>
> For now the kernel only reads TDMR related global metadata fields for
> module initialization. All these fields are 16-bits, and the kernel
> only supports reading 16-bits fields.
>
> KVM will need to read a bunch of non-TDMR related metadata to create and
> run TDX guests. It's essential to provide a generic metadata read
> infrastructure which supports reading all 8/16/32/64 bits element sizes.
>
> Extend the metadata read to support reading all these element sizes.
>
> Signed-off-by: Kai Huang <kai.huang@intel.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> arch/x86/virt/vmx/tdx/tdx.c | 59 +++++++++++++++++++++++++------------
> arch/x86/virt/vmx/tdx/tdx.h | 2 --
> 2 files changed, 40 insertions(+), 21 deletions(-)
>
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index eb208da4ff63..a19adc898df6 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -271,23 +271,35 @@ static int read_sys_metadata_field(u64 field_id, u64 *data)
> return 0;
> }
>
> -static int read_sys_metadata_field16(u64 field_id,
> - int offset,
> - void *stbuf)
> +/* Return the metadata field element size in bytes */
> +static int get_metadata_field_bytes(u64 field_id)
> {
> - u16 *st_member = stbuf + offset;
> + /*
> + * TDX supports 8/16/32/64 bits metadata field element sizes.
> + * TDX module determines the metadata element size based on the
> + * "element size code" encoded in the field ID (see the comment
> + * of MD_FIELD_ID_ELE_SIZE_CODE macro for specific encodings).
> + */
> + return 1 << MD_FIELD_ID_ELE_SIZE_CODE(field_id);
> +}
> +
> +static int stbuf_read_sys_metadata_field(u64 field_id,
> + int offset,
> + int bytes,
> + void *stbuf)
> +{
> + void *st_member = stbuf + offset;
> u64 tmp;
> int ret;
>
> - if (WARN_ON_ONCE(MD_FIELD_ID_ELE_SIZE_CODE(field_id) !=
> - MD_FIELD_ID_ELE_SIZE_16BIT))
> + if (WARN_ON_ONCE(get_metadata_field_bytes(field_id) != bytes))
> return -EINVAL;
>
> ret = read_sys_metadata_field(field_id, &tmp);
> if (ret)
> return ret;
>
> - *st_member = tmp;
> + memcpy(st_member, &tmp, bytes);
>
> return 0;
> }
> @@ -295,11 +307,30 @@ static int read_sys_metadata_field16(u64 field_id,
> 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) }
> + .offset = offsetof(_struct, _member), \
> + .size = sizeof(typeof(((_struct *)0)->_member)) }
> +
> +static int read_sys_metadata(struct field_mapping *fields, int nr_fields,

The first parameter should be "const struct field_mapping *fields".

Juergen

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