Prior to this change both functions returned 0 for success, -1 for failure
and +1 to indicate that an exception was injected into the guest.
The numerical value of ERESTART also happens to be -1 so when these functions
returned -1 it had to be translated to a positive errno value to prevent the
VM_RUN ioctl from being inadvertently restarted. This made it easy to introduce
bugs when writing emulation code.
Fix this by adding an 'int *guest_fault' parameter and setting it to '1' if
an exception was delivered to the guest. The return value is 0 or EFAULT so
no additional translation is needed.
Reviewed by: tychon
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D2428
Keep track of the next instruction to be executed by the vcpu as 'nextrip'.
As a result the VM_RUN ioctl no longer takes the %rip where a vcpu should
start execution.
Also, instruction restart happens implicitly via 'vm_inject_exception()' or
explicitly via 'vm_restart_instruction()'. The APIs behave identically in
both kernel and userspace contexts. The main beneficiary is the instruction
emulation code that executes in both contexts.
bhyve(8) VM exit handlers now treat 'vmexit->rip' and 'vmexit->inst_length'
as readonly:
- Restarting an instruction is now done by calling 'vm_restart_instruction()'
as opposed to setting 'vmexit->inst_length' to 0 (e.g. emulate_inout())
- Resuming vcpu at an arbitrary %rip is now done by setting VM_REG_GUEST_RIP
as opposed to changing 'vmexit->rip' (e.g. vmexit_task_switch())
Differential Revision: https://reviews.freebsd.org/D1526
Reviewed by: grehan
MFC after: 2 weeks
change 0 means success and non-zero means failure.
This also helps to eliminate VMEXIT_POWEROFF and VMEXIT_RESET as return values
from VM-exit handlers.
CR: D480
Reviewed by: grehan, jhb
The faulting instruction needs to be restarted when the exception handler
is done handling the fault. bhyve now does this correctly by setting
'vmexit[vcpu].inst_length' to zero so the %rip is not advanced.
A minor complication is that the fault injection APIs are used by instruction
emulation code that is shared by vmm.ko and bhyve. Thus the argument that
refers to 'struct vm *' in kernel or 'struct vmctx *' in userspace needs to
be loosely typed as a 'void *'.
to 16. This is arbitrary and is used to ensure that a vcpu goes back into
the vm_run() loop to process interrupts or rendezvous events in a timely
fashion.
Found with: Coverity Scan
CID: 1216436
fault on the destination buffer.
Prior to this change a page fault would be detected in vm_copyout(). This
was done after the I/O port access was done. If the I/O port access had
side-effects (e.g. reading the uart FIFO) then restarting the instruction
would result in incorrect behavior.
Fix this by validating the guest linear address before doing the I/O port
emulation. If the validation results in a page fault exception being injected
into the guest then the instruction can now be restarted without any
side-effects.
API function 'vie_calculate_gla()'.
While the current implementation is simplistic it forms the basis of doing
segmentation checks if the guest is in 32-bit protected mode.
of the guest linear address space. These APIs in turn use a new ioctl
'VM_GLA2GPA' to convert the guest linear address to guest physical.
Use the new copyin/copyout APIs when emulating ins/outs instruction in
bhyve(8).
'struct vm_guest_paging'.
Check for canonical addressing in vmm_gla2gpa() and inject a protection
fault into the guest if a violation is detected.
If the page table walk is restarted in vmm_gla2gpa() then reset 'ptpphys' to
point to the root of the page tables.
the UART FIFO.
The emulation is constrained in a number of ways: 64-bit only, doesn't check
for all exception conditions, limited to i/o ports emulated in userspace.
Some of these constraints will be relaxed in followup commits.
Requested by: grehan
Reviewed by: tychon (partially and a much earlier version)
to a virtual machine then we implicitly create COM1 and COM2 ISA devices.
Prior to this change the only way of attaching a COM port to the virtual
machine was by presenting it as a PCI device that is mapped at the legacy
I/O address 0x3F8 or 0x2F8.
There were some issues with the original approach:
- It did not work at all with UEFI because UEFI will reprogram the PCI device
BARs and remap the COM1/COM2 ports at non-legacy addresses.
- OpenBSD GENERIC kernel does not create a /dev/console because it expects
the uart device at the legacy 0x3F8/0x2F8 address to be an ISA device.
- It was functional with a FreeBSD guest but caused the console to appear
on /dev/ttyu2 which was not intuitive.
The uart emulation is now independent of the bus on which it resides. Thus it
is possible to have uart devices on the PCI bus in addition to the legacy
COM1/COM2 devices behind the LPC bus.
The command line option to attach ISA COM1/COM2 ports to a virtual machine is
"-s <bus>,lpc -l com1,stdio".
The command line option to create a PCI-attached uart device is:
"-s <bus>,uart[,stdio]"
The command line option to create PCI-attached COM1/COM2 device is:
"-S <bus>,uart[,stdio]". This style of creating COM ports is deprecated.
Discussed with: grehan
Reviewed by: grehan
Submitted by: Tycho Nightingale (tycho.nightingale@pluribusnetworks.com)
M share/examples/bhyve/vmrun.sh
AM usr.sbin/bhyve/legacy_irq.c
AM usr.sbin/bhyve/legacy_irq.h
M usr.sbin/bhyve/Makefile
AM usr.sbin/bhyve/uart_emul.c
M usr.sbin/bhyve/bhyverun.c
AM usr.sbin/bhyve/uart_emul.h
M usr.sbin/bhyve/pci_uart.c
M usr.sbin/bhyve/pci_emul.c
M usr.sbin/bhyve/inout.c
M usr.sbin/bhyve/pci_emul.h
M usr.sbin/bhyve/inout.h
AM usr.sbin/bhyve/pci_lpc.c
AM usr.sbin/bhyve/pci_lpc.h
- Respect the MEMEN and PORTEN bits in the command register
- Allow the guest to reprogram the address decoded by the BAR
Submitted by: Gopakumar T
Obtained from: NetApp
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
