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| author | Robin Murphy <robin.murphy@arm.com> | 2026-07-27 13:03:28 +0100 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2026-08-02 10:04:52 +0000 |
| commit | 91038c83a250f1a6d49c199db2aaafea882af6c7 (patch) | |
| tree | eb65ce4f1905147b6f62178364314a8fe3ecfc32 | |
| parent | a86c36163c9722545d27e92bdad8418fdcaa8b1d (diff) | |
| download | linux-next-91038c83a250f1a6d49c199db2aaafea882af6c7.tar.gz linux-next-91038c83a250f1a6d49c199db2aaafea882af6c7.zip | |
arm64: Add override for MMFR1.HAFDBS
In general it might be nice to have the ability to disable hardware
access/dirty bit management for debugging or performance comparison
purposes without having to rebuild the kernel. However once FEAT_HAFT
comes into the picture we also start to have a real functional concern
where the decision to use HAFT based on the boot CPUs can prevent SVA
or late-onlining if SMMUs/CPUs are later found to lack HAFT support.
To that end, add the appropriate MMFR1 override, with an easy "nohaft"
alias for the significant case, partly since the feature/field naming
isn't the most obvious, but also so it could potentially be redirected
in future if someone wanted to attempt a higher-level means of turning
off just HAFT usage independently from FEAT_HDBSS.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 3 | ||||
| -rw-r--r-- | arch/arm64/kernel/pi/idreg-override.c | 2 |
2 files changed, 5 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index b5493a7f8f22..7f23e5b8dc44 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -565,6 +565,9 @@ Kernel parameters arm64.nogcs [ARM64] Unconditionally disable Guarded Control Stack support + arm64.nohaft [ARM64] Unconditionally disable Hardware managed Access + Flag for Table descriptors support + arm64.nomops [ARM64] Unconditionally disable Memory Copy and Memory Set instructions support diff --git a/arch/arm64/kernel/pi/idreg-override.c b/arch/arm64/kernel/pi/idreg-override.c index bc57b290e5e7..0e051fec5afe 100644 --- a/arch/arm64/kernel/pi/idreg-override.c +++ b/arch/arm64/kernel/pi/idreg-override.c @@ -64,6 +64,7 @@ static const struct ftr_set_desc mmfr1 __prel64_initconst = { .override = &id_aa64mmfr1_override, .fields = { FIELD("vh", ID_AA64MMFR1_EL1_VH_SHIFT, mmfr1_vh_filter), + FIELD("hafdbs", ID_AA64MMFR1_EL1_HAFDBS_SHIFT, NULL), {} }, }; @@ -246,6 +247,7 @@ static const struct { { "arm64.nomte", "id_aa64pfr1.mte=0" }, { "nokaslr", "arm64_sw.nokaslr=1" }, { "rodata=off", "arm64_sw.rodataoff=1" }, + { "arm64.nohaft", "id_aa64mmfr1.hafdbs=2" }, { "arm64.nolva", "id_aa64mmfr2.varange=0" }, { "arm64.no32bit_el0", "id_aa64pfr0.el0=1" }, { "arm64.nompam", "id_aa64pfr0.mpam=0 id_aa64pfr1.mpam_frac=0" }, |