kconfig: build-in hardware RNG drivers

[lucab]

As of 1772.0.0, our kernel config enables support for hardware random number generators and builds a couple of drivers as modules (CONFIG_HW_RANDOM_VIRTIO and CONFIG_HW_RANDOM_TIMERIOMEM in commonconfig). In order to speed up entropy gathering at early boot (and hopefully sidestep #2429 and similar issues), it would be convenient to build in the most common drivers.

From a quick look around, this would be my proposed list:

CONFIG_HW_RANDOM_VIRTIO=y
CONFIG_HW_RANDOM_CAVIUM=y
CONFIG_HW_RANDOM_VIA=y
CONFIG_HW_RANDOM_INTEL=y
CONFIG_HW_RANDOM_AMD=y

Two additional sidenotes:

• timeriomem-rng is not available on any of the platforms we support, thus it can be safely disabled
• in order to properly use virtio-rng the host needs to pass -device virtio-rng-pci

[glevand]

Probably want to include HW_RANDOM_HISI for their arm64 server chips.

[glevand]

Current configs give this.

arm64-kernel-config
CONFIG_HW_RANDOM_TIMERIOMEM=m
CONFIG_HW_RANDOM_VIRTIO=m
CONFIG_HW_RANDOM_MSM=y
CONFIG_HW_RANDOM_XGENE=y
CONFIG_HW_RANDOM_CAVIUM=y
CONFIG_HW_RANDOM_MTK=y
CONFIG_HW_RANDOM_TPM=y

amd64-kernel-config
CONFIG_HW_RANDOM_TIMERIOMEM=m
CONFIG_HW_RANDOM_VIRTIO=m

[bgilbert]

HW_RANDOM_HISI depends on ARCH_HISI, which we don't set.

I agree that timeriomem is unlikely to be used anywhere, but it's cheap to keep building it as a module and will avoid any accidental breakage.

coreos/scripts#813 enables -device virtio-rng-pci in coreos_production_qemu.sh. We could do the same for kola, but it seems safer to continue to test instances that don't have special provisions for obtaining entropy.

[bgilbert]

Fixed in coreos/coreos-overlay#3231.

[bgilbert]

This should be fixed in alpha 1786.0.1, due shortly.