[PATCH v5 0/5] random,x86,kvm: Rework arch RNG seeds and get some from kvm

[Andy Lutomirski]

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

It also re-works the way that architectural random data is fed into
random.c's pools.  I added a new arch hook called arch_get_rng_seed.
The default implementation is more or less the same as the current
code, except that random_get_entropy is now called unconditionally.

x86 gets a custom arch_get_rng_seed.  It will use KVM_GET_RNG_SEED
if available, and, if it does anything, it will log the number of
bits collected from each available architectural source.  If more
paravirt seed sources show up, it will be a natural place to add
them.

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

Changes from v4:
 - Got rid of the RDRAND behavior change.  If this series is accepted,
   I may resend it separately, but I think it's an unrelated issue.
 - Fix up the changelog entries -- I misunderstood how the old code
   worked.
 - Avoid lots of failed attempts to use KVM_GET_RNG_SEED if it's not
   available.

Changes from v3:
 - Other than KASLR, the guest pieces are completely rewritten.
   Patches 2-4 have essentially nothing in common with v2.

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: Add and use arch_get_rng_seed
  x86,random: Add an x86 implementation of arch_get_rng_seed
  x86,random,kvm: Use KVM_GET_RNG_SEED in arch_get_rng_seed
  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/archrandom.h    |  6 +++
 arch/x86/include/asm/kvm_guest.h     |  9 +++++
 arch/x86/include/asm/processor.h     | 21 ++++++++--
 arch/x86/include/uapi/asm/kvm_para.h |  2 +
 arch/x86/kernel/Makefile             |  2 +
 arch/x86/kernel/archrandom.c         | 74 ++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/kvm.c                | 10 +++++
 arch/x86/kvm/cpuid.c                 |  3 +-
 arch/x86/kvm/x86.c                   |  4 ++
 drivers/char/random.c                | 14 +++++--
 include/linux/random.h               | 40 +++++++++++++++++++
 14 files changed, 212 insertions(+), 7 deletions(-)
 create mode 100644 arch/x86/kernel/archrandom.c

-- 
1.9.3

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