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    SubjectRe: [PATCH v19 004/130] x86/virt/tdx: Support global metadata read for all element sizes
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    On Mon, 2024-02-26 at 15:32 +0100, Juergen Gross wrote:
    > 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".
    >
    >

    Indeed. :-)
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