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arm64: Add override for WFxT

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Add an override for WFxT support within ID_AA64ISAR2_EL1 to allow
it to be disabled using the new arm64.nowfxt command line parameter.

This accompanies the idle=nop param introduced in a previous patch
series [1] in dealing with misbehaving WFI and WFIT instructions on
Apple Silicon SoCs, and eases debugging of other quirky WFxT
implementations.

Link[1]: https://lore.kernel.org/all/20260804-arm64-idle-param-v3-1-d10f8159062b@cyberchaos.dev/
Suggested-by: Will Deacon <will@kernel.org>
Signed-off-by: Yureka Lilian <yureka@cyberchaos.dev>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Yureka Lilian 2026-09-11 19:02:10 +02:00 committed by Will Deacon
parent bb756b11ad
commit baaa9b126b
2 changed files with 5 additions and 0 deletions
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3
Documentation/admin-guide/kernel-parameters.txt
View File

@ -589,6 +589,9 @@ Kernel parameters
arm64.nosve [ARM64] Unconditionally disable Scalable Vector
Extension support
arm64.nowfxt [ARM64] Unconditionally disable Wait For Event with
Timeout and Wait For Interrupt with Timeout support
ataflop= [HW,M68k]
atarimouse= [HW,MOUSE] Atari Mouse

2
arch/arm64/kernel/pi/idreg-override.c
View File

@ -186,6 +186,7 @@ static const struct ftr_set_desc isar2 __prel64_initconst = {
.name = "id_aa64isar2",
.override = &id_aa64isar2_override,
.fields = {
FIELD("wfxt", ID_AA64ISAR2_EL1_WFxT_SHIFT, NULL),
FIELD("gpa3", ID_AA64ISAR2_EL1_GPA3_SHIFT, NULL),
FIELD("apa3", ID_AA64ISAR2_EL1_APA3_SHIFT, NULL),
FIELD("mops", ID_AA64ISAR2_EL1_MOPS_SHIFT, NULL),
@ -254,6 +255,7 @@ static const struct {
"id_aa64isar1.api=0 id_aa64isar1.apa=0 "
"id_aa64isar2.gpa3=0 id_aa64isar2.apa3=0" },
{ "arm64.nomops", "id_aa64isar2.mops=0" },
{ "arm64.nowfxt", "id_aa64isar2.wfxt=0" },
{ "arm64.nomte", "id_aa64pfr1.mte=0" },
{ "nokaslr", "arm64_sw.nokaslr=1" },
{ "rodata=off", "arm64_sw.rodataoff=1" },