id = 2662
title = "powerpc: MSR_ILE bit must not be restored in rfi"
state = "opened"
created_at = "2024-11-08T13:02:02.816Z"
closed_at = "n/a"
labels = ["kind::Bug", "target: ppc", "workflow::Patch available"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/2662"
host-os = "n/a"
host-arch = "n/a"
qemu-version = "n/a"
guest-os = "n/a"
guest-arch = "n/a"
description = """On processors that implement the MSR_ILE bit (that is, G4 and prior), the MSR_ILE bit is not restored by the `rfi` instruction.

qemu, however, does restore this bit from `srr1`.

Some ppcel operating systems rely on MSR_ILE not being restored by `rfi`, for example, Windows NT when taking a syscall."""
reproduce = "n/a"
additional = """Patch provided: [rfi_msr_ile.patch](/uploads/aa661fc8bcbb47585ff63f8e4ebb38ba/rfi_msr_ile.patch)

The correct behaviour for G4 and prior is performed for later processors too. Given PPC970 and later have that bit documented as reserved, this should not be a problem."""