There is slight update from AMD , relevant part for you:
*AMD Microcode Updates for GPZ Variant 2/Spectre*
In addition, microcode updates with our recommended mitigations addressing
Variant 2 (Spectre) have been released to our customers and ecosystem partners
for AMD processors dating back to the first “Bulldozer” core products introduced
AMD customers will be able to install the microcode by downloading BIOS updates
provided by PC and server manufacturers and motherboard providers. Please check
with your provider for the latest updates.
Unfortnately, I dont know where to get that microcode. Any ideas?
And also, it changed in  the claims that IBPB should be made on context switch.