#Yes, maybe. Yes, you may be able to use/abuse (you choose what word fits best) the BACKUP feature of an HSM to extract the plain text version of a private key.
At least in cases where the backup/restore procedure is documented to allow this.
And at least in the case of the "Nitrokey HSM"/"SmartCard-HSM" this is in fact possible because everything about it is open source and there is no hardware to stop you from using/abusing that backup/restore feature.
Details here:
- Remy van Elst, 2016-07-13, Decrypt/Extract Nitrokey HSM/SmartCard-HSM RSA private keys (Archived here.)
#But... Let me says this in summary: while this may be possible technically, it goes against the very reason of existence of an HSM. Namely: What's inside, STAYS inside! -- What you're trying to do sounds sketchy and dangerous. -- I agree with what Steffen said: If your HSM is too slow: get a bigger HSM. Either as a box, or as a service such as Cloudflare's "Keyless SSL".