Running an MS-DOS 6.22 image with qemu-kvm on a RedHat Linux OS, I
noticed the guest OS becomes hung and my dmesg gets spammed with
set_cr0: #GP, set PG flag with a clear PE flag
That message appears to be the linux kernel's kvm emulator griping about
Paging Enable bit being enabled while the Protection Enable bit is set
for real mode. (The Intel manual says this should be a protection
fault).
The program that causes this has the DOS/4GW DOS extender runtime
compiled into it.
I found that when I don't load the EMM386.EXE memory manager, the
problem doesn't occur.
Here's a kvmtrace segment of when things are not working:
0 (+ 0) IO_WRITE vcpu = 0x00000000 pid = 0x00001997 [ port =
0x0070, size = 1 ]
28471049668815 (+ 4000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049671815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x0000004e, rip = 0x00000000 00002a18 ]
0 (+ 0) PAGE_FAULT vcpu = 0x00000000 pid = 0x00001997 [
errorcode = 0x00000000, virt = 0x00000000 0001ba28 ]
28471049675815 (+ 4000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049678815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x0000004e, rip = 0x00000000 00000334 ]
0 (+ 0) PAGE_FAULT vcpu = 0x00000000 pid = 0x00001997 [
errorcode = 0x00000000, virt = 0x00000000 00019344 ]
28471049681815 (+ 3000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049685815 (+ 4000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x00000000, rip = 0x00000000 000002a7 ]
0 (+ 0) CR_READ vcpu = 0x00000000 pid = 0x00001997 [ CR# = 0,
value = 0x00000000 80000011 ]
28471049688815 (+ 3000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049691815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x00000010, rip = 0x00000000 000002ae ]
0 (+ 0) LMSW vcpu = 0x00000000 pid = 0x00001997 [ value =
0x80000011 ]
28471049696815 (+ 5000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049699815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x0000004e, rip = 0x00000000 00005593 ]
0 (+ 0) PAGE_FAULT vcpu = 0x00000000 pid = 0x00001997 [
errorcode = 0x00000000, virt = 0x00000000 000262e3 ]
28471049703815 (+ 4000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049706815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x0000004e, rip = 0x00000000 000044d6 ]
0 (+ 0) PAGE_FAULT vcpu = 0x00000000 pid = 0x00001997 [
errorcode = 0x00000000, virt = 0x00000000 00025226 ]
28471049709815 (+ 3000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049713815 (+ 4000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x0000004e, rip = 0x00000000 000055c0 ]
0 (+ 0) PAGE_FAULT vcpu = 0x00000000 pid = 0x00001997 [
errorcode = 0x00000002, virt = 0x00000000 00024f79 ]
28471049717815 (+ 4000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049721815 (+ 4000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x00000000, rip = 0x00000000 00002a69 ]
0 (+ 0) CR_READ vcpu = 0x00000000 pid = 0x00001997 [ CR# = 0,
value = 0x00000000 80000011 ]
28471049723815 (+ 2000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049726815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x00000010, rip = 0x00000000 00002a73 ]
0 (+ 0) LMSW vcpu = 0x00000000 pid = 0x00001997 [ value =
0x80000010 ]
28471049781815 (+ 55000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049784815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x0000004e, rip = 0x00000000 00001fb8 ]
0 (+ 0) PAGE_FAULT vcpu = 0x00000000 pid = 0x00001997 [
errorcode = 0x00000000, virt = 0x00000000 00022d08 ]
28471049788815 (+ 4000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049792815 (+ 4000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x0000007b, rip = 0x00000000 00001fd6 ]
0 (+ 0) IO_WRITE vcpu = 0x00000000 pid = 0x00001997 [ port =
0x0020, size = 1 ]
28471049794815 (+ 2000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049797815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x0000007b, rip = 0x00000000 00001fd9 ]
0 (+ 0) IO_READ vcpu = 0x00000000 pid = 0x00001997 [ port =
0x0020, size = 1 ]
28471049800815 (+ 3000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049803815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x0000004e, rip = 0x00000000 00001f70 ]
0 (+ 0) PAGE_FAULT vcpu = 0x00000000 pid = 0x00001997 [
errorcode = 0x00000000, virt = 0x00000000 0001a072 ]
28471049807815 (+ 4000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049811815 (+ 4000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x00000000, rip = 0x00000000 00002a69 ]
0 (+ 0) CR_READ vcpu = 0x00000000 pid = 0x00001997 [ CR# = 0,
value = 0x00000000 80000011 ]
28471049815815 (+ 4000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049818815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x00000010, rip = 0x00000000 00002a73 ]
0 (+ 0) LMSW vcpu = 0x00000000 pid = 0x00001997 [ value =
0x80000010 ]
28471049840815 (+ 22000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049844815 (+ 4000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x0000007b, rip = 0x00000000 00001fd6 ]
0 (+ 0) IO_WRITE vcpu = 0x00000000 pid = 0x00001997 [ port =
0x0020, size = 1 ]
28471049846815 (+ 2000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049849815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x0000007b, rip = 0x00000000 00001fd9 ]
0 (+ 0) IO_READ vcpu = 0x00000000 pid = 0x00001997 [ port =
0x0020, size = 1 ]
28471049851815 (+ 2000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049855815 (+ 4000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x00000000, rip = 0x00000000 00002a69 ]
0 (+ 0) CR_READ vcpu = 0x00000000 pid = 0x00001997 [ CR# = 0,
value = 0x00000000 80000011 ]
28471049858815 (+ 3000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049861815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x00000010, rip = 0x00000000 00002a73 ]
0 (+ 0) LMSW vcpu = 0x00000000 pid = 0x00001997 [ value =
0x80000010 ]
28471049882815 (+ 21000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049885815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x0000007b, rip = 0x00000000 00001fd6 ]
0 (+ 0) IO_WRITE vcpu = 0x00000000 pid = 0x00001997 [ port =
0x0020, size = 1 ]
28471049887815 (+ 2000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049890815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x0000007b, rip = 0x00000000 00001fd9 ]
0 (+ 0) IO_READ vcpu = 0x00000000 pid = 0x00001997 [ port =
0x0020, size = 1 ]
28471049892815 (+ 2000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049896815 (+ 4000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x00000000, rip = 0x00000000 00002a69 ]
0 (+ 0) CR_READ vcpu = 0x00000000 pid = 0x00001997 [ CR# = 0,
value = 0x00000000 80000011 ]
28471049900815 (+ 4000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049903815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x00000010, rip = 0x00000000 00002a73 ]
0 (+ 0) LMSW vcpu = 0x00000000 pid = 0x00001997 [ value =
0x80000010 ]
28471049933815 (+ 30000) VMENTRY vcpu = 0x00000000 pid =
0x00001997
28471049936815 (+ 3000) VMEXIT vcpu = 0x00000000 pid =
0x00001997 [ exitcode = 0x0000007b, rip = 0x00000000 00001fd6 ]
To me it appears EMM386.EXE enables paging, and the DOS/4GW DOS extender
tries to manipulate the PE bit in CR0 with LMSW but doesn't succeed.
These programs appear to work fine in VMWare and on real hardware.
Any ideas on how to make EMM386.EXE and the DOS/$GW extender work in
qemu-kvm?
Regards,
Andy
