vmm/amd64: port illumos#14485: bhyve nees better cpuid control

[rosenfeld_grumpf.hope-2000.org]

Summary

This is a port of this bhyve improvements coming from illumos:

14485 bhyve needs better cpuid control
https://www.illumos.org/issues/14485

This adds vmm kernel support for overriding the CPUID information for
a guest.

This does not include the bhyve tests added with illumos#14485 since
FreeBSD lacks the bhyve test suite. This does also not contain any
libvmmapi/bhyve userspace code to make this feature actually useful.

[corvink]

sys/amd64/include/vmm.h

819

837

sys/amd64/vmm/vmm_cpuid.c

28

This shouldn't be required anymore.

578

This could be split into a separate commit to make it easier to review and merge earlier if you like to.

sys/amd64/vmm/vmm_dev_machdep.c

505–522

That's checked by vm_set_cpuid too. I would prefer checking this stuff once.

[emaste]

sys/amd64/vmm/vmm_cpuid.c

2

578

In general if this is a bug fix or otherwise an improvement that can stand alone I would indeed do it in a separate commit (that may be MFC'd to stable branches independent of or earlier than the full new functionality).

[rosenfeld_grumpf.hope-2000.org]

sys/amd64/vmm/vmm_dev_machdep.c

505–522

I think it's better to keep both checks. In particular, I think the ioctl() handler should always validate the parameters it gets from userspace. In addition to that, vm_set_cpuid() doing its own basic sanity checks is useful if it's ever called from a different context, which it very well may be if I continue to improve the CPUID support as I have recently suggested.

All that being said, another point to consider here is that this is working and reviewed code that's been shipping in illumos for a few years. There's very little gained from introducing a difference to the origin here that has no actual benefit such as fixing a real bug, but it's a pain the neck for porting changes in either direction.

[rosenfeld_grumpf.hope-2000.org]

Remove illumos#16223 from this change.

[markj]

sys/amd64/vmm/intel/vmx.c

2661

Continuing lines should be indented by four spaces.

sys/amd64/vmm/vmm_cpuid.c

31

These should be grouped with the existing copyright statement at the beginning of the file.

44

Spurious newline.

180

The caller asserts that last_std != NULL, but why is that true? It seems to me that userspace could construct a cpuid configuration where it's possible to return NULL, resulting in a null pointer dereference.

sys/amd64/vmm/vmm_dev_machdep.c

64

Extra newline here.

468

Rather than having the explicit bzero call, just use the M_ZERO malloc flag.