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 -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
