Nvidia disclosed 122.8M SpaceX shares, i.e. around $21B stake.
The position traces back to Nvidia's investment in xAI, whose shareholders received SpaceX equity when SpaceX acquired the AI company.
SpaceX is simultaneously becoming a large Nvidia customer, with Musk saying its data centers will be built exclusively on Nvidia and compute capacity could approach 10GW by end-2027.
To note, Alphabet (Google) also is hugely exposed to SpaceX on both sides of the transaction.
Google has agreed to pay SpaceX $920M per month for access to roughly 110,000 Nvidia GPUs, while Alphabet itself owns about $94.1B of SpaceX at June-end, so Google can outsource the infrastructure risk while Alphabet still participates in the economics of the supplier.
AMD is in a strangely asymmetric position. It owns SpaceX equity (3.31M shares, worth about $565.5M at June-end), yet SpaceX has committed its future data-center buildout to Nvidia, so AMD can participate in SpaceX's valuation upside while Nvidia captures the accelerator revenue.