KVM: arm64: Support FF-A 1.2

Hi,

The FF-A 1.2 specification introduces a new SEND_DIRECT2 ABI which
allows registers x4-x17 to be used for the message payload. This patch
set prevents the host from using a lower FF-A version than what has
already been negotiated with the hypervisor. This is necessary because
the hypervisor does not have the necessary compatibility paths to
translate from the hypervisor FF-A version to a previous version.

Support for FF-A 1.2 in the hypervisor is added as a precursor to the
addition of the FFA_MSG_SEND_DIRECT_REQ2 messaging interface. Notably,
this patch updates all smc calls to use SMCCC 1.2 as it makes it simpler
to support interfaces that need to accept more than 8 arguments and/or
return more than 4 values. The list of optional/unsupported interfaces
was updated to reflect additions in FF-A 1.2.

Tested by booting Android under QEMU and loading Trusty as the guest
VM and observing the SEND_DIRECT2 ABI being used successfully during
guest boot.

Changes in v9:
- 2/7 -> 2/6: Updated explanatory comment in ffa_set_retval
- 4/7 -> 4/6: Restore to v7: Mark FFA_MSG_SEND_DIRECT_REQ2 unsupported
- 5/7 -> 5/6: Added Acked-by: Will Deacon <will@kernel.org>
- 6/7 -> 6/6: Added Acked-by: Will Deacon <will@kernel.org>
- 7/7:        Dropped
- Link to v8: https://lore.kernel.org/r/20250719-virtio-msg-ffa-v8-0-03...

Changes in v8:
- 2/5 -> 2/7: Use func_id argument to distinguish SMC32/SMC64. Update rationale.
- 4/5 -> 4/7: Split up 4/5: Add optional FF-A 1.2 interfaces
- 4/5 -> 5/7: Split up 4/5: Mask FFA_RXTX_MAP minium buffer size in a2. Don't check MBZ bits.
- 4/5 -> 6/7: Remainder of 4/5: Bump supported version to FF-A 1.2
- 5/5 -> 7/7: Don't check src id in do_ffa_direct_msg2
- Link to v7: https://lore.kernel.org/r/20250701-virtio-msg-ffa-v7-0-99...

Changes in v7:
- 0/6:        Revised cover letter slightly
- 4/6:        ffa_call_supported: Clarify optional interfaces
              hyp_ffa_post_init: Sanitize MBZ bits in x2 and x3
              address nit: use GENMASK
- Link to v6: https://lore.kernel.org/r/20250627-virtio-msg-ffa-v6-0-8c... 

Changes since v5:
- 3/6 -> 2/5: Merged with parent patch as they were closely related
              Don't rename variables from "res" to "regs" to avoid churn
              Update and clarify reasoning for condition added to ffa_set_retval
              Adopt style suggested by Marc when passing regs to arm_smccc_1_2_smc
              Fix inadvertent duplicate statements in ffa_{map,unmap}_hyp_buffers
- Link to v5: https://lore.kernel.org/r/20250619-virtio-msg-ffa-v5-0-41...

Changes since v4:
- 1/5 -> 1/6: Added Acked-by: Will Deacon <will@kernel.org>y
              Reworded patch subject and description
- 2/5:        Dropped patch: zero x4-x7 in ffa_set_retval
-        2/6: New: use SMCCC 1.2 during hyp init
-        3/6: New: use SMCCC 1.2 in host FF-A handler
- 3/5 -> 4/6: No change; can revisit denylist design in later patchset
              Added Acked-by: Will Deacon <will@kernel.org>
- 4/5 -> 5/6: No change
- 5/5 -> 6/6: No change
- Link to v4: https://lore.kernel.org/r/20250516-virtio-msg-ffa-v4-0-58...

Changes since v3:
- all:        Remove Signed-off-by: Per Larsen <perl@immunant.com>
- 2/5:        Split out from 2/3, zero x4-x7 in set_ffa_retval
- 3/5:        Split out from 2/3, Mark FFA_NOTIFICATION_* calls as
              unsupported
- 2/3 -> 4/5: Drop ffa_get_hypervisor_version, access hyp_ffa_version
              directly when version negotiation is complete.
- 3/3 -> 5/5: Call ffa_to_smccc_1_2_error directly in
              do_do_ffa_direct_msg2
              Push call to ffa_call_needs_smccc_1_2 lower down by adding
              ffa_get_func_id and ffa_set_retval_smccc_1_x.
              Drop ffa_to_smccc_1_2_regs and ffa_to_smccc_1_2_regs_prop
              as they are no longer used.
- Link to v3: https://lore.kernel.org/r/20250513-virtio-msg-ffa-v3-0-d6... 

Changes since v2:
- 2/3: Removed files added by mistake.
       Add and use ffa_get_hypervisor_version to access hyp_ffa_version
- 3/3: Use ffa_get_hypervisor_version to access hyp_ffa_version safely
- Link to v2: https://lore.kernel.org/r/20250508-virtio-msg-ffa-v2-0-ed...

Changes since v1:
- 1/3: Simplify commit message; drop long comment in do_ffa_version
- 2/3: Correct use of Co-developed-by: footer
       s/arm_smccc_1_2_smc_fallback/arm_smccc_1_x_smc/
       Always access hyp_ffa_version w/lock held
       Remove superfluous comments in ffa_call_supported
       Add and use FFA_FEAT_RXTX_MIN_SZ_MASK instead of constant
       Add FFA_PARTITION_INFO_GET_REGS to calls that require SMCCC 1.2
- 3/3: Always access hyp_ffa_version w/lock held
       Correct formatting

Thanks,
Per Larsen

--
2.49.0

---
Per Larsen (6):
      KVM: arm64: Correct return value on host version downgrade attempt
      KVM: arm64: Use SMCCC 1.2 for FF-A initialization and in host handler
      KVM: arm64: Mark FFA_NOTIFICATION_* calls as unsupported
      KVM: arm64: Mark optional FF-A 1.2 interfaces as unsupported
      KVM: arm64: Mask response to FFA_FEATURE call
      KVM: arm64: Bump the supported version of FF-A to 1.2

 arch/arm64/kvm/hyp/nvhe/Makefile |   1 +
 arch/arm64/kvm/hyp/nvhe/ffa.c    | 215 ++++++++++++++++++++++++++-------------
 include/linux/arm_ffa.h          |   1 +
 3 files changed, 144 insertions(+), 73 deletions(-)
---
base-commit: 4b290aae788e06561754b28c6842e4080957d3f7
change-id: 20250506-virtio-msg-ffa-22af72c92150

Best regards,
-- 
Per Larsen <perlarsen@google.com>