arm64: errata: Expand speculative SSBS workaround once more

A number of Arm Ltd CPUs suffer from errata whereby an MSR to the SSBS
special-purpose register does not affect subsequent speculative
instructions, permitting speculative store bypassing for a window of
time.

We worked around this for a number of CPUs in commits:

* 7187bb7d ("arm64: errata: Add workaround for Arm errata 3194386 and 3312417")
* 75b3c43e ("arm64: errata: Expand speculative SSBS workaround")
* 145502cac7ea70b5 ("arm64: errata: Expand speculative SSBS workaround (again)")

Since then, a (hopefully final) batch of updates have been published,
with two more affected CPUs. For the affected CPUs the existing
mitigation is sufficient, as described in their respective Software
Developer Errata Notice (SDEN) documents:

* Cortex-A715 (MP148) SDEN v15.0, erratum 3456084
  https://developer.arm.com/documentation/SDEN-2148827/1500/

* Neoverse-N3 (MP195) SDEN v5.0, erratum 3456111
  https://developer.arm.com/documentation/SDEN-3050973/0500/

Enable the existing mitigation by adding the relevant MIDRs to
erratum_spec_ssbs_list, and update silicon-errata.rst and the
Kconfig text accordingly.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20240930111705.3352047-3-mark.rutland@arm.comSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

Documentation/arch/arm64/silicon-errata.rst

@@ -146,6 +146,8 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A715     | #2645198        | ARM64_ERRATUM_2645198       |
 +----------------+-----------------+-----------------+-----------------------------+
+| ARM            | Cortex-A715     | #3456084        | ARM64_ERRATUM_3194386       |
++----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A720     | #3456091        | ARM64_ERRATUM_3194386       |
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A725     | #3456106        | ARM64_ERRATUM_3194386       |
@@ -186,6 +188,8 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Neoverse-N2     | #3324339        | ARM64_ERRATUM_3194386       |
 +----------------+-----------------+-----------------+-----------------------------+
+| ARM            | Neoverse-N3     | #3456111        | ARM64_ERRATUM_3194386       |
++----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Neoverse-V1     | #1619801        | N/A                         |
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Neoverse-V1     | #3324341        | ARM64_ERRATUM_3194386       |

arch/arm64/Kconfig

@@ -1097,6 +1097,7 @@ config ARM64_ERRATUM_3194386
 	  * ARM Cortex-A78C erratum 3324346
 	  * ARM Cortex-A78C erratum 3324347
 	  * ARM Cortex-A710 erratam 3324338
+	  * ARM Cortex-A715 errartum 3456084
 	  * ARM Cortex-A720 erratum 3456091
 	  * ARM Cortex-A725 erratum 3456106
 	  * ARM Cortex-X1 erratum 3324344
@@ -1107,6 +1108,7 @@ config ARM64_ERRATUM_3194386
 	  * ARM Cortex-X925 erratum 3324334
 	  * ARM Neoverse-N1 erratum 3324349
 	  * ARM Neoverse N2 erratum 3324339
+	  * ARM Neoverse-N3 erratum 3456111
 	  * ARM Neoverse-V1 erratum 3324341
 	  * ARM Neoverse V2 erratum 3324336
 	  * ARM Neoverse-V3 erratum 3312417

arch/arm64/kernel/cpu_errata.c

@@ -439,6 +439,7 @@ static const struct midr_range erratum_spec_ssbs_list[] = {
 	MIDR_ALL_VERSIONS(MIDR_CORTEX_A78),
 	MIDR_ALL_VERSIONS(MIDR_CORTEX_A78C),
 	MIDR_ALL_VERSIONS(MIDR_CORTEX_A710),
+	MIDR_ALL_VERSIONS(MIDR_CORTEX_A715),
 	MIDR_ALL_VERSIONS(MIDR_CORTEX_A720),
 	MIDR_ALL_VERSIONS(MIDR_CORTEX_A725),
 	MIDR_ALL_VERSIONS(MIDR_CORTEX_X1),
@@ -449,6 +450,7 @@ static const struct midr_range erratum_spec_ssbs_list[] = {
 	MIDR_ALL_VERSIONS(MIDR_CORTEX_X925),
 	MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N1),
 	MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N2),
+	MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N3),
 	MIDR_ALL_VERSIONS(MIDR_NEOVERSE_V1),
 	MIDR_ALL_VERSIONS(MIDR_NEOVERSE_V2),
 	MIDR_ALL_VERSIONS(MIDR_NEOVERSE_V3),