Re: [PATCH 5/5] x86/virt/tdx: Export global metadata read infrastructure

From: Huang, Kai
Date: Mon May 06 2024 - 07:35:27 EST


On Fri, 2024-05-03 at 18:31 +0000, Edgecombe, Rick P wrote:
> On Fri, 2024-05-03 at 14:17 +1200, Huang, Kai wrote:
> >
> >
> > On 3/05/2024 12:21 pm, Edgecombe, Rick P wrote:
> > > On Sat, 2024-03-02 at 00:20 +1300, Kai Huang wrote:
> > > > 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.
> > > >
> > > Could 2 be a static inline in a helper, and then only have one export?
> >
> > I assume you were thinking about making 2) call the 1), so we don't need
> > to export 2).
> >
> > This is not feasible due to:
> >
> > a). 1) must 'struct tdx_metadata_field_mapping' table as input, and for
> > that we need to ues the TDX_SYSINFO_MAP() macro to define a structure
> > for just one 'u64' and define a 'struct tdx_metadata_field_mapping'
> > table which only has one element for that.
> >
> > b). TDX_SYSINFO_MAP() macro actually doesn't support taking a metadata
> > field "variable", but can only support using the name of the metadata field.
> >
> > However we can try to make 1) as a wrapper of 2).  But this would
> > require some change to the patch 4.
> >
> > I'll reply separately to patch 4 and you can take a look whether that is
> > better.
>
> Having one export would be nice. Yea, since the multiple field processing
> version just loops anyway, doing it like you propose seems reasonable.

Sure I'll switch to use the new code as replied in patch 4.