The branch main has been updated by andrew:
URL:
https://cgit.FreeBSD.org/src/commit/?id=ea6865bb78c5ac007a50f3d06a8e745052f745a0
commit ea6865bb78c5ac007a50f3d06a8e745052f745a0
Author: Andrew Turner <and...@freebsd.org>
AuthorDate: 2024-10-18 09:17:22 +0000
Commit: Andrew Turner <and...@freebsd.org>
CommitDate: 2024-10-21 12:23:16 +0000
arm64: Update how we handle SpecSEI
The ID_AA64MMFR1_EL0.SpecSEI field needs to use MRS_HIGHER to get the
largest value from all CPUs. This is because it indicates when an
exception might happen when it's non-zero and can't happen when zero.
As indicating something that might happen even when it can't is safer
use MRS_HIGHER to handle this field.
Reviewed by: imp
Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D47126
---
sys/arm64/arm64/identcpu.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/sys/arm64/arm64/identcpu.c b/sys/arm64/arm64/identcpu.c
index 834b0c5493b4..f4d297e7d9bc 100644
--- a/sys/arm64/arm64/identcpu.c
+++ b/sys/arm64/arm64/identcpu.c
@@ -1283,7 +1283,14 @@ static const struct mrs_field id_aa64mmfr1_fields[] = {
MRS_FIELD(ID_AA64MMFR1, ETS, false, MRS_LOWER, 0, id_aa64mmfr1_ets),
MRS_FIELD(ID_AA64MMFR1, TWED, false, MRS_LOWER, 0, id_aa64mmfr1_twed),
MRS_FIELD(ID_AA64MMFR1, XNX, false, MRS_LOWER, 0, id_aa64mmfr1_xnx),
- MRS_FIELD(ID_AA64MMFR1, SpecSEI, false, MRS_LOWER, 0,
+ /*
+ * SpecSEI != 0 indicates the CPU might generate an external abort
+ * under speculation, while 0 indicates it can't happen. It's safer
+ * to incorrectly indicate it might happen when it can't rather than
+ * say it can't happen when it could. As such use the largest value
+ * found in the system.
+ */
+ MRS_FIELD(ID_AA64MMFR1, SpecSEI, false, MRS_HIGHER, 0,
id_aa64mmfr1_specsei),
MRS_FIELD(ID_AA64MMFR1, PAN, false, MRS_LOWER, 0, id_aa64mmfr1_pan),
MRS_FIELD(ID_AA64MMFR1, LO, false, MRS_LOWER, 0, id_aa64mmfr1_lo),
