The most suitable mechanism to communicate the status of major portfolio risks to stakeholders is:

The risk management plan describes the approach and processes for managing risk; it is a planning document, not a status communication vehicle.

Portfolio performance reports are specifically designed to communicate status information across all portfolio dimensions, including risk status, to a broad stakeholder audience. They synthesize data into a format appropriate for stakeholder consumption and are distributed according to the communications management plan, making them the most suitable mechanism for this purpose.

Steering committee meeting minutes capture decisions and discussions from a specific meeting; they are not a proactive communication mechanism for all stakeholders.

Portfolio risk register updates are working documents for the portfolio team's risk tracking; they are not formatted or intended as stakeholder communications.