Date: Tue, 25 Jun 2019 03:26:32 +0000 From: bugzilla-noreply@freebsd.org To: virtualization@FreeBSD.org Subject: [Bug 238794] LAPIC register test failure with OpenBSD 6.5-snapshot guest Message-ID: <bug-238794-27103@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=238794 Bug ID: 238794 Summary: LAPIC register test failure with OpenBSD 6.5-snapshot guest Product: Base System Version: 11.3-RELEASE Hardware: amd64 OS: Any Status: New Severity: Affects Some People Priority: --- Component: bhyve Assignee: virtualization@FreeBSD.org Reporter: jason@tubnor.net OpenBSD has just imported LLVM 8.0 into -current and the way the compiler builds code to test the LAPIC register has changed (though still valid according to Intel documentation). guenther@ from the OpenBSD project provided some insights based on information provided. Below is an extract from the email thread: > 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. The full thread can be found here: https://marc.info/?l=openbsd-bugs&m=156142900518812&w=2 -- You are receiving this mail because: You are the assignee for the bug.help
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