Previously this was done by the caller of 'svm_launch()' after it returned.
This works fine as long as no code is executed in the interim that depends
on pcpu data.
The dtrace probe 'fbt:vmm:svm_launch:return' broke this assumption because
it calls 'dtrace_probe()' which in turn relies on pcpu data.
Reported by: avg
MFC after: 1 week
devmem is used to represent MMIO devices like the boot ROM or a VESA framebuffer
where doing a trap-and-emulate for every access is impractical. devmem is a
hybrid of system memory (sysmem) and emulated device models.
devmem is mapped in the guest address space via nested page tables similar
to sysmem. However the address range where devmem is mapped may be changed
by the guest at runtime (e.g. by reprogramming a PCI BAR). Also devmem is
usually mapped RO or RW as compared to RWX mappings for sysmem.
Each devmem segment is named (e.g. "bootrom") and this name is used to
create a device node for the devmem segment (e.g. /dev/vmm/testvm.bootrom).
The device node supports mmap(2) and this decouples the host mapping of
devmem from its mapping in the guest address space (which can change).
Reviewed by: tychon
Discussed with: grehan
Differential Revision: https://reviews.freebsd.org/D2762
MFC after: 4 weeks
"sleeping" state. This is done by forcing the vcpu to transition to "idle"
by returning to userspace with an exit code of VM_EXITCODE_REQIDLE.
MFC after: 2 weeks
- 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
code segment base address.
Also if an instruction doesn't support a mod R/M (modRM) byte, don't
be concerned if the CPU is in real mode.
Reviewed by: neel
- fix warning about comparison of 'uint8_t v_tpr >= 0' always being true.
- fix error triggered by an empty clobber list in the inline assembly for
"clgi" and "stgi"
- fix error when compiling "vmload %rax", "vmrun %rax" and "vmsave %rax". The
gcc assembler does not like the explicit operand "%rax" while the clang
assembler requires specifying the operand "%rax". Fix this by encoding the
instructions using the ".byte" directive.
Reported by: julian
MFC after: 1 week
VM_INJECT_EXCEPTION ioctl. However it morphed into other uses like keeping
track pending exceptions for a vcpu. This in turn causes confusion because
some fields in 'struct vm_exception' like 'vcpuid' make sense only in the
ioctl context. It also makes it harder to add or remove structure fields.
Fix this by using 'struct vm_exception' only to communicate information
from userspace to vmm.ko when injecting an exception.
Also, add a field 'restart_instruction' to 'struct vm_exception'. This
field is set to '1' for exceptions where the faulting instruction is
restarted after the exception is handled.
MFC after: 1 week
emulated or when the vcpu incurs an exception. This matches the CPU behavior.
Remove special case code in HLT processing that was clearing the interrupt
shadow. This is now redundant because the interrupt shadow is always cleared
when the vcpu is resumed after an instruction is emulated.
Reported by: David Reed (david.reed@tidalscale.com)
MFC after: 2 weeks
vm_inject_exception(). This fixes the issue that 'exception.cpuid' is
uninitialized when calling 'vm_inject_exception()'.
However, in practice this change is a no-op because vm_inject_exception()
does not use 'exception.cpuid' for anything.
Reported by: Coverity Scan
CID: 1261297
MFC after: 3 days
"hw.vmm.trace_guest_exceptions". To enable this feature set the tunable
to "1" before loading vmm.ko.
Tracing the guest exceptions can be useful when debugging guest triple faults.
Note that there is a performance impact when exception tracing is enabled
since every exception will now trigger a VM-exit.
Also, handle machine check exceptions that happen during guest execution
by vectoring to the host's machine check handler via "int $18".
Discussed with: grehan
MFC after: 2 weeks
options to display some key VMCB fields.
The set of valid options that can be passed to bhyvectl now depends on the
processor type. AMD-specific options are identified by a "--vmcb" or "--avic"
in the option name. Intel-specific options are identified by a "--vmcs" in
the option name.
Submitted by: Anish Gupta (akgupt3@gmail.com)
- Host registers are now stored on the stack instead of a per-cpu host context.
- Host %FS and %GS selectors are not saved and restored across VMRUN.
- Restoring the %FS/%GS selectors was futile anyways since that only updates
the low 32 bits of base address in the hidden descriptor state.
- GS.base is properly updated via the MSR_GSBASE on return from svm_launch().
- FS.base is not used while inside the kernel so it can be safely ignored.
- Add function prologue/epilogue so svm_launch() can be traced with Dtrace's
FBT entry/exit probes. They also serve to save/restore the host %rbp across
VMRUN.
Reviewed by: grehan
Discussed with: Anish Gupta (akgupt3@gmail.com)
- CR2
- CR0, CR3, CR4 and EFER
- GDT/IDT base/limit fields
- CS/DS/ES/SS selector/base/limit/attrib fields
The caching can be further restricted via the tunable 'hw.vmm.svm.vmcb_clean'.
Restructure the code such that the fields above are only modified in a single
place. This makes it easy to invalidate the VMCB cache when any of these fields
is modified.
Keep track of NMI blocking by enabling the IRET intercept on a successful
vNMI injection. The NMI blocking condition is cleared when the handler
executes an IRET and traps back into the hypervisor.
Don't inject NMI if the processor is in an interrupt shadow to preserve the
atomic nature of "STI;HLT". Take advantage of this and artificially set the
interrupt shadow to prevent NMI injection when restarting the "iret".
Reviewed by: Anish Gupta (akgupt3@gmail.com), grehan
Get rid of unused 'svm_feature' from the softc.
Get rid of the redundant 'vcpu_cnt' checks in svm.c. There is a similar check
in vmm.c against 'vm->active_cpus' before the AMD-specific code is called.
Submitted by: Anish Gupta (akgupt3@gmail.com)
processor. Briefly, the hypervisor sets V_INTR_VECTOR to the APIC vector
and sets V_IRQ to 1 to indicate a pending interrupt. The hardware then takes
care of injecting this vector when the guest is able to receive it.
Legacy PIC interrupts are still delivered via the event injection mechanism.
This is because the vector injected by the PIC must reflect the state of its
pins at the time the CPU is ready to accept the interrupt.
Accesses to the TPR via %CR8 are handled entirely in hardware. This requires
that the emulated TPR must be synced to V_TPR after a #VMEXIT.
The guest can also modify the TPR via the memory mapped APIC. This requires
that the V_TPR must be synced with the emulated TPR before a VMRUN.
Reviewed by: Anish Gupta (akgupt3@gmail.com)
VM-exit and ultimately on whether nRIP is valid. This allows us to update
the %rip after the emulation is finished so any exceptions triggered during
the emulation will point to the right instruction.
Don't attempt to handle INS/OUTS VM-exits unless the DecodeAssist capability
is available. The effective segment field in EXITINFO1 is not valid without
this capability.
Add VM_EXITCODE_SVM to flag SVM VM-exits that cannot be handled. Provide the
VMCB fields exitinfo1 and exitinfo2 as collateral to help with debugging.
Provide a SVM VM-exit handler to dump the exitcode, exitinfo1 and exitinfo2
fields in bhyve(8).
Reviewed by: Anish Gupta (akgupt3@gmail.com)
Reviewed by: grehan
- Don't enable the HLT intercept by default. It will be enabled by bhyve(8)
if required. Prior to this change HLT exiting was always enabled making
the "-H" option to bhyve(8) meaningless.
- Recognize a VM exit triggered by a non-maskable interrupt. Prior to this
change the exit would be punted to userspace and the virtual machine would
terminate.
instruction bytes in the VMCB on a nested page fault. This is useful because
it saves having to walk the guest page tables to fetch the instruction.
vie_init() now takes two additional parameters 'inst_bytes' and 'inst_len'
that map directly to 'vie->inst[]' and 'vie->num_valid'.
The instruction emulation handler skips calling 'vmm_fetch_instruction()'
if 'vie->num_valid' is non-zero.
The use of this capability can be turned off by setting the sysctl/tunable
'hw.vmm.svm.disable_npf_assist' to '1'.
Reviewed by: Anish Gupta (akgupt3@gmail.com)
Discussed with: grehan
window exiting. This simply involves setting V_IRQ and enabling the VINTR
intercept. This instructs the CPU to trap back into the hypervisor as soon
as an interrupt can be injected into the guest. The pending interrupt is
then injected via the traditional event injection mechanism.
Rework vcpu interrupt injection so that Linux guests now idle with host cpu
utilization close to 0%.
Reviewed by: Anish Gupta (earlier version)
Discussed with: grehan
Provide APIs svm_enable_intercept()/svm_disable_intercept() to add/delete
VMCB intercepts. These APIs ensure that the VMCB state cache is invalidated
when intercepts are modified.
Each intercept is identified as a (index,bitmask) tuple. For e.g., the
VINTR intercept is identified as (VMCB_CTRL1_INTCPT,VMCB_INTCPT_VINTR).
The first 20 bytes in control area that are used to enable intercepts
are represented as 'uint32_t intercept[5]' in 'struct vmcb_ctrl'.
Modify svm_setcap() and svm_getcap() to use the new APIs.
Discussed with: Anish Gupta (akgupt3@gmail.com)
Prior to this change an ASID was hard allocated to a guest and shared by all
its vcpus. The meant that the number of VMs that could be created was limited
to the number of ASIDs supported by the CPU. It was also inefficient because
it forced a TLB flush on every VMRUN.
With this change the number of guests that can be created is independent of
the number of available ASIDs. Also, the TLB is flushed only when a new ASID
is allocated.
Discussed with: grehan
Reviewed by: Anish Gupta (akgupt3@gmail.com)
