[PATCH v3 0/5] ARM: arm64: Add SMCCC TRNG entropy service

[Andre Przywara]

Hi,

an update to v2 with some fixes and a few tweaks. Ard's patch [1] should
significantly reduce the frequency of arch_get_random_seed_long() calls,
not sure if that is enough the appease the concerns about the
potentially long latency of SMC calls. I also dropped the direct
arch_get_random() call in KVM for the same reason. An alternative could
be to just use the SMC in the _early() versions, but then we would lose
the SMCCC entropy source for the periodic reseeds. This could be mitigated
by using a hwrng driver [2] and rngd.
The only other non-minor change to v2 is the addition of using the SMCCC
call in the _early() variant. For a changelog see below.

Sudeep: patch 1/5 is a prerequisite for all other patches, which
themselves could be considered separate and need to go via different trees.
If we could agree on that one now and get that merged, it would help the
handling of the other patches going forward.

Cheers,
Andre
==============================

The ARM architected TRNG firmware interface, described in ARM spec
DEN0098[3], defines an ARM SMCCC based interface to a true random number
generator, provided by firmware.

This series collects all the patches implementing this in various
places: as a user feeding into the ARCH_RANDOM pool, both for ARM and
arm64, and as a service provider for KVM guests.

Patch 1 introduces the interface definition used by all three entities.
Patch 2 prepares the Arm SMCCC firmware driver to probe for the
interface. This patch is needed to avoid a later dependency on *two*
patches (there might be a better solution to this problem).

Patch 3 implements the ARM part, patch 4 is the arm64 version.
The final patch 5 adds support to provide random numbers to KVM guests.

This was tested on:
- QEMU -kernel (no SMCCC, regression test)
- Juno w/ prototype of the h/w Trusted RNG support
- mainline KVM (SMCCC, but no TRNG: regression test)
- ARM and arm64 KVM guests, using the KVM service in patch 5/5

Based on v5.10-rc3, please let me know if I should rebased on something
else. A git repo is accessible at:
https://gitlab.arm.com/linux-arm/linux-ap/-/commits/smccc-trng/v3/

Cheers,
Andre

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2020-November/615446.html
[2] https://gitlab.arm.com/linux-arm/linux-ap/-/commit/87e3722f437
[3] https://developer.arm.com/documentation/den0098/latest/

Changelog v2 ... v3:
- ARM: fix compilation with randconfig
- arm64: use SMCCC call also in arch_get_random_seed_long_early()
- KVM: comment on return value usage
- KVM: use more interesting UUID (enjoy, Marc!)
- KVM: use bitmaps instead of open coded long arrays
- KVM: drop direct usage of arch_get_random() interface

Changelog "v1" ... v2:
- trigger ARCH_RANDOM initialisation from the SMCCC firmware driver
- use a single bool in smccc.c to hold the initialisation state for arm64
- handle endianess correctly in the KVM provider

Andre Przywara (2):
  firmware: smccc: Introduce SMCCC TRNG framework
  arm64: Add support for SMCCC TRNG entropy source

Ard Biesheuvel (3):
  firmware: smccc: Add SMCCC TRNG function call IDs
  ARM: implement support for SMCCC TRNG entropy source
  KVM: arm64: implement the TRNG hypervisor call

 arch/arm/Kconfig                    |  4 ++
 arch/arm/include/asm/archrandom.h   | 74 +++++++++++++++++++++++++
 arch/arm64/include/asm/archrandom.h | 79 +++++++++++++++++++++++----
 arch/arm64/include/asm/kvm_host.h   |  2 +
 arch/arm64/kvm/Makefile             |  2 +-
 arch/arm64/kvm/hypercalls.c         |  6 ++
 arch/arm64/kvm/trng.c               | 85 +++++++++++++++++++++++++++++
 drivers/firmware/smccc/smccc.c      |  5 ++
 include/linux/arm-smccc.h           | 31 +++++++++++
 9 files changed, 277 insertions(+), 11 deletions(-)
 create mode 100644 arch/arm/include/asm/archrandom.h
 create mode 100644 arch/arm64/kvm/trng.c

-- 
2.17.1