KVM: arm64: Avoid mismatched accesses to 'struct kvm_nvhe_init_params'

When running with hVHE enabled, ___kvm_hyp_init() calls
__kvm_init_el2_state() on the CPU initialisation path during onlining
and resume from suspend.

In order to avoid clobbering the link register across this call, it is
stashed away in the 'tmp' member of 'struct kvm_nvhe_init_params',
however this save/restore operation is performed with the stage-1 MMU
disabled at EL2 and therefore gives rise to coherency problems because
the field is not aligned or padded to the CWG. For example, a cacheable
write to a physically-adjacent structure sharing the same cacheline
could lead to an eviction and subsequent write-back, overwriting the
saved LR while the incoming CPU is executing __kvm_init_el2_state().

Save the lr in far_el2 and remove the 'tmp' member from
'struct kvm_nvhe_init_params' altogether.

Cc: Oliver Upton <oupton@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Fixes: afa9b48f327c ("KVM: arm64: Shave a few bytes from the EL2 idmap code")
Signed-off-by: Will Deacon <will@kernel.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://patch.msgid.link/20260813131717.5885-1-will@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>

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