Season the tenderloin all over with salt. Refrigerate 4 hours or up to 24 hours. Thirty minutes before roasting remove beef from refrigerator.
Preheat oven to 400 F. Combine mushrooms, rosemary and peppercorns in spice grinder. Grind to a coarse powder. Rub beef with olive oil. Coat all over with porcini rosemary rub.
(Note: Make sure your mushrooms are completely dry and brittle, or they won't willingly grind into powder. If they're at all pliant, you can dry them out in the oven until they break easily.)
Heat 1 tablespoon olive oil in a wide skillet over medium-high heat until shimmering. Add beef and brown on all sides, about 8 minutes. Transfer to a roasting pan. Roast in oven until thermometer inserted in thickest part reads 125 F., about 30 minutes, for medium rare. Remove from oven and transfer to a cutting board. Tent with foil and let stand for 15 minutes.
Carve beef in 1/4 inch slices. Serve with Port Wine Sauce.