[Bug 216003] New: Single stepping Windows 7 bootloader results in Assertion `ret < cpu->num_ases && ret >= 0' failed.

* [Bug 216003] New: Single stepping Windows 7 bootloader results in Assertion `ret < cpu->num_ases && ret >= 0' failed.
@ 2022-05-20  0:54 bugzilla-daemon
  2022-05-29 20:28 ` [Bug 216003] " bugzilla-daemon
  0 siblings, 1 reply; 2+ messages in thread
From: bugzilla-daemon @ 2022-05-20  0:54 UTC (permalink / raw)
  To: kvm

https://bugzilla.kernel.org/show_bug.cgi?id=216003

            Bug ID: 216003
           Summary: Single stepping Windows 7 bootloader results in
                    Assertion `ret < cpu->num_ases && ret >= 0' failed.
           Product: Virtualization
           Version: unspecified
    Kernel Version: 5.17.6-200.fc35.x86_64
          Hardware: Intel
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: kvm
          Assignee: virtualization_kvm@kernel-bugs.osdl.org
          Reporter: ercli@ucdavis.edu
        Regression: No

CPU model: Intel(R) Core(TM) i7-4510U CPU @ 2.00GHz
Host kernel version: 5.17.6-200.fc35.x86_64
Host kernel arch: x86_64
Guest: Windows 7 or Windows 10 BIOS mode boot loader. 32-bits.
This bug still exists if using -machine kernel_irqchip=off
This bug no longer exists if using -accel tcg

How to reproduce:

1. Install Windows 7 or Windows 10 in QEMU. Use MBR and BIOS (i.e. do not use
GPT and UEFI). For example, I installed Windows on a 32G disk, and it results
in around 3 partitions: 50M, 31.5G (this is C:), 450M. Only the MBR header
(around 1 M) and the 50M disk is needed. For example,
https://drive.google.com/uc?id=1mLvKsPSuLbeckwcdnavnQMu8QxOwvX29 can be used to
reproduce this bug. Suppose Windows is installed in w.img.

2. Start QEMU
qemu-system-x86_64 --drive media=disk,file=w.img,format=raw,index=1 -s -S
-enable-kvm

3. Start GDB
gdb --ex 'target remote :::1234' --ex 'hb *0x7c00' --ex c --ex 'si 10000' --ex
q
This GDB command starts from the MBR header and runs 10000 instructions. When I
am reproducing it, running 1000 is enough to reproduce this problem. If this
problem cannot be reproduced, try to increase this number.

4. See error in QEMU:
qemu-system-x86_64: ../hw/core/cpu-sysemu.c:77: cpu_asidx_from_attrs: Assertion
`ret < cpu->num_ases && ret >= 0' failed.
Aborted (core dumped)

Expected behavior: there should not be an assertion error. GDB should be able
to single step a lot of instructions successfully.

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