id = 2578
title = "x86: exception during hardware interrupt pushes wrong error code"
state = "opened"
created_at = "2024-09-19T09:09:25.955Z"
closed_at = "n/a"
labels = ["accel: TCG", "target: i386", "workflow::Patch available"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/2578"
host-os = "- OS/kernel version:"
host-arch = "- QEMU flavor:                 qemu-system-x86_64 qemu-system-i386"
qemu-version = "all"
guest-os = "- OS/kernel version:"
guest-arch = "x86"
description = """Exceptions during IDT traversal push the wrong error code when triggered by a hardware interrupt.
The EXT bit in TCG mode is never set.  However, it works fine in KVM mode as hardware is generating the number."""
reproduce = """1. load a short IDT e.g. with 64 entries
2. trigger a self IPI through the LAPIC with a vector 100
3. the pushed error code is 802 instead of 803."""
additional = """It can be fixed in the lines `raise_exception_err(env, EXCP0D_GPF, intno * 8 + 2);` in `seg_helper.c` 
which must include the `is_hw` field when calculating the error number. Something like `intno * 8 + 2 + (is_hw != 0)` 
works here.

Nevertheless, all the other exception cases in the `do_interrupt_*` functions have to set the same bit as well."""