There is slight update from AMD [1], 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 in 2011. 

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 [2] the claims that IBPB should be made on context switch.


[1] https://www.amd.com/en/corporate/security-updates
[2] https://developer.amd.com/wp-content/resources/Architecture_Guidelines_Update_Indirect_Branch_Control.pdf