[PATCH v2 0/5] ARM: arm64: Add SMCCC TRNG entropy service

[Andre Przywara]

The ARM architected TRNG firmware interface, described in ARM spec
DEN0098[1], 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.

Compared to the initial posts, this version:
- triggers the ARCH_RANDOM initialisation from the SMCCC firmware driver
- uses a single bool in smccc.c to hold the initialisation state for arm64
- handles endianess correctly in the KVM provider

This was tested on:
- QEMU -kernel (no SMCCC, regression test)
- Juno w/ standard firmware (SMCCC, but no TRNG: regression test)
- Juno w/ "fake TRNG" firmware (to verify "random" numbers)
- 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-rc2, 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/v2/

Cheers,
Andre

[1] https://developer.arm.com/documentation/den0098/latest/

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 | 63 +++++++++++++++++---
 arch/arm64/include/asm/kvm_host.h   |  2 +
 arch/arm64/kvm/Makefile             |  2 +-
 arch/arm64/kvm/hypercalls.c         |  6 ++
 arch/arm64/kvm/trng.c               | 91 +++++++++++++++++++++++++++++
 drivers/firmware/smccc/smccc.c      |  5 ++
 include/linux/arm-smccc.h           | 31 ++++++++++
 9 files changed, 270 insertions(+), 8 deletions(-)
 create mode 100644 arch/arm/include/asm/archrandom.h
 create mode 100644 arch/arm64/kvm/trng.c

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2.17.1