On Mon, 24 Jun 2019, Jason Tubnor wrote: > Following daily snapshots, I have hit a bug that was introduced between > 6.5-current #61 and 6.5-current #66 (not sure if it was related to the LLVM > upgrade). > > Reference system is bhyve on FreeBSD 11.2 with an OpenBSD guest. #61 boots > fine and runs as expected. However, #66 get to the following point and the > guest terminates: ... > Below is output from bhyve.log: > > rdmsr to register 0xc80 on vcpu 0 > Failed to emulate instruction [0xf7 0x04 0x25 0x00 0xd3 0xd1 0x81 0x00 0x10 > 0x00 0x00 0x74 0x08 0xf3 0x90] at 0xffffffff817648f0
According to objdump -d, that's: f7 04 25 00 d3 d1 81 testl $0x1000,0xffffffff81d1d300 00 10 00 00 74 08 je <forward some> f3 90 pause That's testing the LAPIC ICRLO, a memory-mapped register. Previously, the compiler generated code like this: 8b 0c 25 00 63 cf 81 mov 0xffffffff81cf6300,%ecx f7 c1 00 10 00 00 test $0x1000,%ecx 74 09 je <forward some> f3 90 pause where it loaded the LAPIC register into %ecx and then tested that value; now it combines them and does a direct test. Congrats, that's legal according to Intel (reportedly, Windows will use SSE(!) instructions to read LAPIC registers), so this seems like a bug in Bhyve. Philip Guenther
