FROMLIST: arm64: mte: move register initialization to C

If FEAT_MTE2 is disabled via the arm64.nomte command line argument on a
CPU that claims to support FEAT_MTE2, the kernel will use Tagged Normal
in the MAIR. If we interpret arm64.nomte to mean that the CPU does not
in fact implement FEAT_MTE2, setting the system register like this may
lead to UNSPECIFIED behavior. Fix it by arranging for MAIR to be set
in the C function cpu_enable_mte which is called based on the sanitized
version of the system register.

There is no need for the rest of the MTE-related system register
initialization to happen from assembly, with the exception of TCR_EL1,
which must be set to include at least TBI1 because the secondary CPUs
access KASan-allocated data structures early. Therefore, make the TCR_EL1
initialization unconditional and move the rest of the initialization to
cpu_enable_mte so that we no longer have a dependency on the unsanitized
ID register value.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Signed-off-by: Evgenii Stepanov <eugenis@google.com>
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/linux-arm-kernel/20220825021532.1175943-1-eugenis@google.com/
Bug: 239834217
X-PCC-To: Catalin Marinas <catalin.marinas@arm.com>
X-PCC-Cc: Evgenii Stepanov <eugenis@google.com>, Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>, Vincenzo Frascino <vincenzo.frascino@arm.com>, Andrey Konovalov <andreyknvl@gmail.com>, Mark Brown <broonie@kernel.org>, Linux ARM <linux-arm-kernel@lists.infradead.org>, LKML <linux-kernel@vger.kernel.org>
Change-Id: I0733c8aa54bbf412761f49d93532ca509414b6b4