Don't use VM when ppGTT is invalid/unassigned

[jbeich]

VM wasn't ported on FreeBSD but "create" ioctl succeeds, confusing NEO whether VM can be used.

freebsd/drm-kmod#24

[MichalMrozek]

can you add Unit Level Tests?

[HoppeMateusz]

Please fix commit message following the rules:
https://github.com/intel/compute-runtime/blob/master/CONTRIBUTING.md#2-certificate-of-origin

You will have to add empty line after commit message, and Signed-off-by:

[jbeich]

can you add Unit Level Tests?

2 years ago when porting NEO I've spent ~2 additional days (2x more than IGC + NEO without tests) trying to unbreak build of unit tests but eventually gave up by adding SKIP_ALL_ULT (SKIP_UNIT_TESTS nowadays) and removing related patches to ease the maintenance. IIRC, there were many dependencies not just on Linux features but GNU libc specifics which made me wonder if the tests supported musl or bionic.

[jbeich]

You will have to add empty line after commit message, and Signed-off-by:

Done.

[HoppeMateusz]

You will have to add empty line after commit message, and Signed-off-by:

Done.

Thanks for the update, commit message has been verified.

[zzdanowicz]

GNU libc specifics which made me wonder if the tests supported musl or bionic.

Can you tell what were the problem with glibc? FreeBSD does not have it, so its equivalent of libc might be different - asking out of curiosity?

[HoppeMateusz]

We usually require unit tests for every change, but in this case, due to small change size and justified problems, we decided to waive this requirement and will merge the PR.

Thanks for contribution

[HoppeMateusz]

merged as bb6ed00

[jbeich]

Confirmed downstream.