[PATCH 4/5] arm64: errata: Unify speculative SSBS errata logic
Mark Rutland
mark.rutland at arm.com
Mon Jun 3 04:18:11 PDT 2024
Cortex-X4 erratum 3194386 and Neoverse-V3 erratum 3312417 are identical,
with duplicate Kconfig text and some unsightly ifdeffery. While we try
to share code behind CONFIG_ARM64_WORKAROUND_SPECULATIVE_SSBS, having
separate options results in a fair amount of boilerplate code, and this
will only get worse as we expand the set of affected CPUs.
To reduce this boilerplate, unify the two behind a common Kconfig
option. This removes the duplicate text and Kconfig logic, and removes
the need for the intermediate ARM64_WORKAROUND_SPECULATIVE_SSBS option.
The set of affected CPUs is described as a list so that this can easily
be extended.
I've used ARM64_ERRATUM_3194386 (matching the Neoverse-V3 erratum ID) as
the common option, matching the way we use ARM64_ERRATUM_1319367 to
cover Cortex-A57 erratum 1319537 and Cortex-A72 erratum 1319367.
Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: James Morse <james.morse at arm.com>
Cc: Will Deacon <wilL at kernel.org>
---
Documentation/arch/arm64/silicon-errata.rst | 2 +-
arch/arm64/Kconfig | 29 +++------------------
arch/arm64/include/asm/cpucaps.h | 2 +-
arch/arm64/kernel/cpu_errata.c | 8 ++----
arch/arm64/kernel/proton-pack.c | 2 +-
5 files changed, 9 insertions(+), 34 deletions(-)
diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
index eb8af8032c315..59ee2832406c2 100644
--- a/Documentation/arch/arm64/silicon-errata.rst
+++ b/Documentation/arch/arm64/silicon-errata.rst
@@ -158,7 +158,7 @@ stable kernels.
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Neoverse-V1 | #1619801 | N/A |
+----------------+-----------------+-----------------+-----------------------------+
-| ARM | Neoverse-V3 | #3312417 | ARM64_ERRATUM_3312417 |
+| ARM | Neoverse-V3 | #3312417 | ARM64_ERRATUM_3194386 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | MMU-500 | #841119,826419 | N/A |
+----------------+-----------------+-----------------+-----------------------------+
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 5d91259ee7b53..fb31ff9151b9d 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1067,34 +1067,14 @@ config ARM64_ERRATUM_3117295
If unsure, say Y.
-config ARM64_WORKAROUND_SPECULATIVE_SSBS
- bool
-
config ARM64_ERRATUM_3194386
- bool "Cortex-X4: 3194386: workaround for MSR SSBS not self-synchronizing"
- select ARM64_WORKAROUND_SPECULATIVE_SSBS
+ bool "Cortex-X4/Neoverse-V3: workaround for MSR SSBS not self-synchronizing"
default y
help
- This option adds the workaround for ARM Cortex-X4 erratum 3194386.
+ This option adds the workaround for the following errata:
- On affected cores "MSR SSBS, #0" instructions may not affect
- subsequent speculative instructions, which may permit unexepected
- speculative store bypassing.
-
- Work around this problem by placing a speculation barrier after
- kernel changes to SSBS. The presence of the SSBS special-purpose
- register is hidden from hwcaps and EL0 reads of ID_AA64PFR1_EL1, such
- that userspace will use the PR_SPEC_STORE_BYPASS prctl to change
- SSBS.
-
- If unsure, say Y.
-
-config ARM64_ERRATUM_3312417
- bool "Neoverse-V3: 3312417: workaround for MSR SSBS not self-synchronizing"
- select ARM64_WORKAROUND_SPECULATIVE_SSBS
- default y
- help
- This option adds the workaround for ARM Neoverse-V3 erratum 3312417.
+ * ARM Cortex-X4 erratum 3194386
+ * ARM Neoverse-V3 erratum 3312417
On affected cores "MSR SSBS, #0" instructions may not affect
subsequent speculative instructions, which may permit unexepected
@@ -1108,7 +1088,6 @@ config ARM64_ERRATUM_3312417
If unsure, say Y.
-
config CAVIUM_ERRATUM_22375
bool "Cavium erratum 22375, 24313"
default y
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 7529c02639332..a6e5b07b64fd5 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -59,7 +59,7 @@ cpucap_is_possible(const unsigned int cap)
case ARM64_WORKAROUND_REPEAT_TLBI:
return IS_ENABLED(CONFIG_ARM64_WORKAROUND_REPEAT_TLBI);
case ARM64_WORKAROUND_SPECULATIVE_SSBS:
- return IS_ENABLED(CONFIG_ARM64_WORKAROUND_SPECULATIVE_SSBS);
+ return IS_ENABLED(CONFIG_ARM64_ERRATUM_3194386);
}
return true;
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 828be635e7e1d..5fbe14dc607f0 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -432,14 +432,10 @@ static const struct midr_range erratum_spec_unpriv_load_list[] = {
};
#endif
-#ifdef CONFIG_ARM64_WORKAROUND_SPECULATIVE_SSBS
-static const struct midr_range erratum_spec_ssbs_list[] = {
#ifdef CONFIG_ARM64_ERRATUM_3194386
+static const struct midr_range erratum_spec_ssbs_list[] = {
MIDR_ALL_VERSIONS(MIDR_CORTEX_X4),
-#endif
-#ifdef CONFIG_ARM64_ERRATUM_3312417
MIDR_ALL_VERSIONS(MIDR_NEOVERSE_V3),
-#endif
{}
};
#endif
@@ -741,7 +737,7 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
MIDR_FIXED(MIDR_CPU_VAR_REV(1,1), BIT(25)),
},
#endif
-#ifdef CONFIG_ARM64_WORKAROUND_SPECULATIVE_SSBS
+#ifdef CONFIG_ARM64_ERRATUM_3194386
{
.desc = "ARM errata 3194386, 3312417",
.capability = ARM64_WORKAROUND_SPECULATIVE_SSBS,
diff --git a/arch/arm64/kernel/proton-pack.c b/arch/arm64/kernel/proton-pack.c
index baca47bd443c8..da53722f95d41 100644
--- a/arch/arm64/kernel/proton-pack.c
+++ b/arch/arm64/kernel/proton-pack.c
@@ -567,7 +567,7 @@ static enum mitigation_state spectre_v4_enable_hw_mitigation(void)
* Mitigate this with an unconditional speculation barrier, as CPUs
* could mis-speculate branches and bypass a conditional barrier.
*/
- if (IS_ENABLED(CONFIG_ARM64_WORKAROUND_SPECULATIVE_SSBS))
+ if (IS_ENABLED(CONFIG_ARM64_ERRATUM_3194386))
spec_bar();
return SPECTRE_MITIGATED;
--
2.30.2
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