Per the Intel manuals, CPUID is supposed to unconditionally zero the
upper 32 bits of the involved (rax/rbx/rcx/rdx) registers.
Previously, the emulation would cast pointers to the 64-bit register
values down to `uint32_t`, which while properly manipulating the lower
bits, would leave any garbage in the upper bits uncleared. While no
existing guest OSes seem to stumble over this in practice, the bhyve
emulation should match x86 expectations.
This was discovered through alignment warnings emitted by gcc9, while
testing it against SmartOS/bhyve.
SmartOS bug: https://smartos.org/bugview/OS-8168
Submitted by: Patrick Mooney
Reviewed by: rgrimes
Differential Revision: https://reviews.freebsd.org/D24727
In recent Linux (5.3+) and OpenBSD (6.6+) kernels, and with hosts that
support CPUID 0x15, the local APIC frequency is determined directly
from the reported crystal clock to avoid calibration against the 8254
timer.
However, the local APIC frequency implemented by bhyve is 128MHz, where
most h/w systems report frequencies around 25MHz. This shows up on
OpenBSD guests as repeated keystrokes on the emulated PS2 keyboard
when using VNC, since the kernel's timers are now much shorter.
Fix by reporting all-zeroes for CPUID 0x15. This allows guests to fall
back to using the 8254 to calibrate the local APIC frequency.
Future work could be to compute values returned for 0x15 that would
match the host TSC and bhyve local APIC frequency, though all dependencies
on this would need to be examined (for example, Linux will start using
0x16 for some hosts).
PR: 246321
Reported by: Jason Tubnor (and tested)
Reviewed by: jhb
Approved by: jhb, bz (mentor)
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D24837
vmm's CPUID emulation presented Intel topology information to the guest, but
disabled AMD topology information and in some cases passed through garbage.
I.e., CPUID leaves 0x8000_001[de] were passed through to the guest, but
guest CPUs can migrate between host threads, so the information presented
was not consistent. This could easily be observed with 'cpucontrol -i 0xfoo
/dev/cpuctl0'.
Slightly improve this situation by enabling the AMD topology feature flag
and presenting at least the CPUID fields used by FreeBSD itself to probe
topology on more modern AMD64 hardware (Family 15h+). Older stuff is
probably less interesting. I have not been able to empirically confirm it
is sufficient, but it should not regress anything either.
Reviewed by: araujo (previous version)
Relnotes: sure
Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
- Must-Be-Zero bits cannot be set.
- EFER_LME and EFER_LMA should respect the long mode consistency checks.
- EFER_NXE, EFER_FFXSR, EFER_TCE can be set if allowed by CPUID capabilities.
- Flag an error if guest tries to set EFER_LMSLE since bhyve doesn't enforce
segment limits in 64-bit mode.
MFC after: 2 weeks
- Don't always pass the cpuid request to the current CPU as some nodes
we will emulate purely in software.
- Pass in the APIC ID of the virtual CPU so we can return the proper APIC
ID.
- Always report a completely flat topology with no SMT or multicore.
- Report the CPUID2_HV feature and implement support for the 0x40000000
CPUID level.
- Use existing constants from <machine/specialreg.h> when possible and
use cpu_feature2 when checking for VMX support.
run as a 1/2 CPU guest on an 8.1 bhyve host.
bhyve/inout.c
inout.h
fbsdrun.c
- Rather than exiting on accesses to unhandled i/o ports, emulate
hardware by returning -1 on reads and ignoring writes to unhandled
ports. Support the previous mode by allowing a 'strict' parameter
to be set from the command line.
The 8.1 guest kernel was vastly cut down from GENERIC and had no
ISA devices. Booting GENERIC exposes a massive amount of random
touching of i/o ports (hello syscons/vga/atkbdc).
bhyve/consport.c
dev/bvm/bvm_console.c
- implement a simplistic signature for the bvm console by returning
'bv' for an inw on the port. Also, set the priority of the console
to CN_REMOTE if the signature was returned. This works better in
an environment where multiple consoles are in the kernel (hello syscons)
bhyve/rtc.c
- return 0 for the access to RTC_EQUIPMENT (yes, you syscons)
amd64/vmm/x86.c
x86.h
- hide a bunch more CPUID leaf 1 bits from the guest to prevent
cpufreq drivers from probing.
The next step will be to move CPUID handling completely into
user-space. This will allow the full spectrum of changes from
presenting a lowest-common-denominator CPU type/feature set, to
exposing (almost) everything that the host can support.
Reviewed by: neel
Obtained from: NetApp
vmm.ko - kernel module for VT-x, VT-d and hypervisor control
bhyve - user-space sequencer and i/o emulation
vmmctl - dump of hypervisor register state
libvmm - front-end to vmm.ko chardev interface
bhyve was designed and implemented by Neel Natu.
Thanks to the following folk from NetApp who helped to make this available:
Joe CaraDonna
Peter Snyder
Jeff Heller
Sandeep Mann
Steve Miller
Brian Pawlowski
