From baaa9b126b875b40ffd9356da52c7c871917e5bb Mon Sep 17 00:00:00 2001 From: Yureka Lilian Date: Fri, 11 Sep 2026 19:02:10 +0200 Subject: [PATCH] arm64: Add override for WFxT 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 Signed-off-by: Yureka Lilian Signed-off-by: Will Deacon --- Documentation/admin-guide/kernel-parameters.txt | 3 +++ arch/arm64/kernel/pi/idreg-override.c | 2 ++ 2 files changed, 5 insertions(+) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 68647ff4bdd2..0fe9e36ce61a 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -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 diff --git a/arch/arm64/kernel/pi/idreg-override.c b/arch/arm64/kernel/pi/idreg-override.c index 274bc72ba98d..acaf56234973 100644 --- a/arch/arm64/kernel/pi/idreg-override.c +++ b/arch/arm64/kernel/pi/idreg-override.c @@ -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" },