[PATCH v2 0/3] KVM: arm64: Fixes for SMC64 SYSTEM_RESET2 calls

[Oliver Upton]

This series addresses a couple of issues with how KVM exposes SMC64
calls to its guest. It is currently possible for an AArch32 guest to
discover the SMC64 SYSTEM_RESET2 function (via
PSCI_1_0_FN_PSCI_FEATURES) and even make a call to it. SMCCC does not
allow for 64 bit calls to be made from a 32 bit state.

Patch 1 cleans up the way we filter SMC64 calls in PSCI. Using a switch
with case statements for each possibly-filtered function is asking for
trouble. Instead, pivot off of the bit that indicates the desired
calling convention. This plugs the PSCI_FEATURES hole for SYSTEM_RESET2.

Patch 2 adds a check to the PSCI v1.x call handler in KVM, bailing out
early if the guest is not allowed to use a particular function. This
closes the door on calls to 64-bit SYSTEM_RESET2 from AArch32.

Lastly, patch 3 is a nit to remove a superfluous check in the hopes of
avoiding trouble the next time we raise KVM's PSCI version.

Applies on top of kvmarm/next at commit:

  21ea45784275 ("KVM: arm64: fix typos in comments")

v1: http://lore.kernel.org/r/20220318193831.482349-1-oupton@google.com

v1 -> v2:
 - Collect Acks and Reviews (Reiji, Will)
 - Hoist SMC64 filtering all the way up to kvm_psci_call() (Reiji)

Oliver Upton (3):
  KVM: arm64: Generally disallow SMC64 for AArch32 guests
  KVM: arm64: Actually prevent SMC64 SYSTEM_RESET2 from AArch32
  KVM: arm64: Drop unneeded minor version check from PSCI v1.x handler

 arch/arm64/kvm/psci.c | 31 ++++++++++++++-----------------
 1 file changed, 14 insertions(+), 17 deletions(-)

-- 
2.35.1.894.gb6a874cedc-goog