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arm64: errata: Unify speculative SSBS errata logic

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[ Upstream commit ec768766608092087dfb5c1fc45a16a6f524dee2 ]

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@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20240603111812.1514101-5-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
[ Mark: fix conflicts & renames, drop unneeded cpucaps.h ]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Mark Rutland 2024-08-09 11:17:35 +01:00 committed by Greg Kroah-Hartman
parent 17ff37fe45
commit bf0d247dfb
4 changed files with 8 additions and 32 deletions
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2
Documentation/arm64/silicon-errata.rst
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@ -106,7 +106,7 @@ stable kernels.
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Neoverse-N1 | #1542419 | ARM64_ERRATUM_1542419 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | Neoverse-V3 | #3312417 | ARM64_ERRATUM_3312417 |
| ARM | Neoverse-V3 | #3312417 | ARM64_ERRATUM_3194386 |
+----------------+-----------------+-----------------+-----------------------------+
| ARM | MMU-500 | #841119,826419 | N/A |
+----------------+-----------------+-----------------+-----------------------------+

28
arch/arm64/Kconfig
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@ -691,34 +691,14 @@ config ARM64_ERRATUM_2457168
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

8
arch/arm64/kernel/cpu_errata.c
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@ -364,14 +364,10 @@ static struct midr_range broken_aarch32_aes[] = {
};
#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
@ -583,7 +579,7 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
},
#endif
#ifdef CONFIG_ARM64_WORKAROUND_SPECULATIVE_SSBS
#ifdef CONFIG_ARM64_ERRATUM_3194386
{
.desc = "ARM errata 3194386, 3312417",
.capability = ARM64_WORKAROUND_SPECULATIVE_SSBS,

2
arch/arm64/kernel/proton-pack.c
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@ -583,7 +583,7 @@ 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;