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Diffstat (limited to 'results/classifier/deepseek-2/output/KVM/1658141')
| -rw-r--r-- | results/classifier/deepseek-2/output/KVM/1658141 | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/results/classifier/deepseek-2/output/KVM/1658141 b/results/classifier/deepseek-2/output/KVM/1658141 new file mode 100644 index 000000000..116f34499 --- /dev/null +++ b/results/classifier/deepseek-2/output/KVM/1658141 @@ -0,0 +1,45 @@ + +QEMU's default msrs handling causes Windows 10 64 bit to crash + +Wine uses QEMU to run its conformance test suite on Windows virtual machines. Wine's conformance tests check the behavior of various Windows APIs and verify that they behave as expected. + +One such test checks handling of exceptions down. When run on Windows 10 64 bit in QEMU it triggers a "KMOD_EXCEPTION_NOT_HANDLED" BSOD in the VM. See: +https://bugs.winehq.org/show_bug.cgi?id=40240 + + +To reproduce this bug: +* Pick a Windows 10 64 bit VM on an Intel host. + +* Start the VM. I'm pretty sure any qemu command will do but here's what I used: + qemu-system-x86_64 -machine pc-i440fx-2.1,accel=kvm -cpu core2duo,+nx -m 2048 -hda /var/lib/libvirt/images/wtbw1064.qcow2 + +* Grab the attached source code. The tar file is a bit big at 85KB because I had to include some Wine headers. However the source file proper, exception.c, is only 85 lines, including the LGPL header. + +* Compile the source code with MinGW by typing 'make'. This produces a 32 bit exception.exe executable. I'll attach it for good measure. + +* Put exception.exe on the VM and run it. + + +After investigation it turns out this happens: + * Only for Windows 10 64 bit guests. Windows 10 32 bit and older Windows versions are unaffected. + + * Only on Intel hosts. At least both my Xeon E3-1226 v3 and i7-4790K hosts are impacted but not my Opteron 6128 one. + + * It does not seem to depend on the emulated CPU type: on the Intel hosts this happened with both +core2duo,nx and 'copy the host configuration' and did not depend on the number of emulated cpus/cores. + + * This happened with both QEMU 2.1 and 2.7, and both the 3.16.0 and 4.8.11 Linux kernels, both on Debian 8.6 and Debian Testing. + + +After searching for quite some time I discovered that the kvm kernel module was sneaking the following messages into /var/log/syslog precisely when the BSOD happens: + +Dec 16 13:43:48 vm3 kernel: [ 191.624802] kvm [2064]: vcpu0, guest rIP: 0xfffff803cb3c0bf3 kvm_set_msr_common: MSR_IA32_DEBUGCTLMSR 0x1, nop +Dec 16 13:43:48 vm3 kernel: [ 191.624835] kvm [2064]: vcpu0, guest rIP: 0xfffff803cb3c0c5c unhandled rdmsr: 0x1c9 + +A search on the Internet turned up a post suggesting to change kvm's ignore_msrs setting: + + echo 1 >/sys/module/kvm/parameters/ignore_msrs + +https://www.reddit.com/r/VFIO/comments/42dj7n/some_games_crash_to_biosboot_on_launch/ + +This does actually work and provides a workaround at least. \ No newline at end of file |