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From: Robert Crowston <crowston@protonmail.com>
Reply-To: Robert Crowston <crowston@protonmail.com>
Subject: Single stepping a bhyve guest on AMD64
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I am investigating using the -G flag to attach gdb to a running guest machi=
ne.

It looks like breakpoints and single instruction stepping are not implement=
ed in vmm/amd/svm.c. It seems that it was added to vmm/intel/vmx.c. I spent=
 a little bit of time reading through the AMD64 Architecture Manual; it doe=
sn't seem to provide a direct way to implement this in a way transparent to=
 the guest?

One way to implement single stepping that occurs to me is to set the trap f=
lag in the guest's RFLAGS register, and then intercept each #DB exception i=
n the vmm.

Has anyone looked at this on the AMD side? Any advice?

---
Rob Crowston.