arm64: entry: fold el1_inv() into el1h_64_sync_handler()

arm64: entry: fold el1_inv() into el1h_64_sync_handler()

An unexpected synchronous exception from EL1h could happen at any time,
and for robustness we should treat this as an NMI, making minimal
assumptions about the context the exception was taken from.

Currently el1_inv() assumes we can use enter_from_kernel_mode(), and
also assumes that we should inherit the original DAIF value. Neither of
these are desireable when we take an unexpected exception. Further,
after el1_inv() calls __panic_unhandled(), the remainder of the function
is unreachable, and therefore superfluous.

Let's address this and simplify things by having el1h_64_sync_handler()
call __panic_unhandled() directly, without any of the redundant logic.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Reported-by: Joey Gouly <joey.gouly@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210607094624.34689-16-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>