[PATCH v3 0/5] random,x86,kvm: Add and use MSR_KVM_GET_RNG_SEED

Andy Lutomirski
2014-07-16T21:45:32Z

This introduces and uses a very simple synchronous mechanism to get
/dev/urandom-style bits appropriate for initial KVM PV guest RNG
seeding.

virtio-rng is not suitable for this purpose. It's too difficult to
enumerate for use in early boot (e.g. KASLR, which runs before we
even have an IDT). It also provides /dev/random-style bits, which
means that making guest boot wait for virtio-rng is unacceptably
slow, and doing it asynchronously means that /dev/urandom might
still be predictable when userspace starts.

I sent the corresponding kvm-unit-tests and qemu changes separately.

There's room for bikeshedding on the same arch_get_slow_rng_u64. I
considered arch_get_rng_seed_u64, but that could be confused with
arch_get_random_seed_long, which is not interchangeable.

Changes from v2:
- Bisection fix (patch 2 had a misplaced brace). The final states is
identical to that of v2.
- Improve the 0/5 description a little bit.

Changes from v1:
- Split patches 2 and 3
- Log all arch sources in init_std_data
- Fix the 32-bit kaslr build

Andy Lutomirski (5):
x86,kvm: Add MSR_KVM_GET_RNG_SEED and a matching feature bit
random,x86: Add arch_get_slow_rng_u64
random: Seed pools from arch_get_slow_rng_u64 at startup
random: Log how many bits we managed to seed with in init_std_data
x86,kaslr: Use MSR_KVM_GET_RNG_SEED for KASLR if available

Documentation/virtual/kvm/cpuid.txt | 3 +++
arch/x86/Kconfig | 4 ++++
arch/x86/boot/compressed/aslr.c | 27 +++++++++++++++++++++++++++
arch/x86/include/asm/archslowrng.h | 30 ++++++++++++++++++++++++++++++
arch/x86/include/asm/processor.h | 21 ++++++++++++++++++---
arch/x86/include/uapi/asm/kvm_para.h | 2 ++
arch/x86/kernel/kvm.c | 22 ++++++++++++++++++++++
arch/x86/kvm/cpuid.c | 3 ++-
arch/x86/kvm/x86.c | 4 ++++
drivers/char/random.c | 20 ++++++++++++++++++--
include/linux/random.h | 9 +++++++++
11 files changed, 139 insertions(+), 6 deletions(-)
create mode 100644 arch/x86/include/asm/archslowrng.h

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1.9.3