The helper that updates live page table entries writes a zero entry, invalidates the covered address range from the TLBs, and finally writes the actual entry. This ensures that no TLB conflicts can occur.
Writing the final entry needs to complete before any translations can be performed, as otherwise, the zero entry, which describes an invalid translation, may be observed by the page table walker, resulting in a translation fault. For this reason, the final write is followed by a DSB barrier instruction. However, this barrier will not stall the pipeline, and instruction fetches may still hit this invalid translation, as has been observed and reported by Oliver. To ensure that the new translation is fully active before returning from this helper, we have to insert an ISB barrier as well. Cc: Liming Gao <gaolim...@byosoft.com.cn> Cc: Leif Lindholm <quic_llind...@quicinc.com> Cc: Michael D Kinney <michael.d.kin...@intel.com> Reported-by: Oliver Steffen <ostef...@redhat.com> Tested-by: Oliver Steffen <ostef...@redhat.com> Signed-off-by: Ard Biesheuvel <a...@kernel.org> --- ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibReplaceEntry.S | 1 + 1 file changed, 1 insertion(+) diff --git a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibReplaceEntry.S b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibReplaceEntry.S index 887439bc042f0f16..1f0d8057926933d7 100644 --- a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibReplaceEntry.S +++ b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibReplaceEntry.S @@ -65,6 +65,7 @@ // write updated entry str x1, [x0] dsb nshst + isb .L2_\@: .endm -- 2.39.2 -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#105092): https://edk2.groups.io/g/devel/message/105092 Mute This Topic: https://groups.io/mt/99027974/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
