Asking for "funny" memory sizes sometimes crashes for me. For instance
-m 0.8 or the equivalent -m 838860b. -m 0.7 appears to work.
Should we round memory sizes? How? Where?
$ gdb --args qemu-system-x86_64 -nodefaults --enable-kvm -S -vnc :0 -monitor
stdio -m 0.8
[...]
(gdb) r
Starting program: /home/armbru/bin/upstream-qemu -nodefaults --enable-kvm -S
-vnc :0 -monitor stdio -m 0.8
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
[New Thread 0x7ffff6efe700 (LWP 29525)]
upstream-qemu: /work/armbru/qemu/exec.c:2263: register_subpage: Assertion
`existing->mr->subpage || existing->mr == &io_mem_unassigned' failed.
Program received signal SIGABRT, Aborted.
0x00000033e0835965 in raise () from /lib64/libc.so.6
[...]
(gdb) bt
#0 0x00000033e0835965 in raise () from /lib64/libc.so.6
#1 0x00000033e0837118 in abort () from /lib64/libc.so.6
#2 0x00000033e082e6e2 in __assert_fail_base () from /lib64/libc.so.6
#3 0x00000033e082e792 in __assert_fail () from /lib64/libc.so.6
#4 0x00000000006078fa in register_subpage (section=0x7fffffffd4e0)
at /work/armbru/qemu/exec.c:2263
#5 0x0000000000607b55 in cpu_register_physical_memory_log (section=
0x7fffffffd6a0, readonly=false) at /work/armbru/qemu/exec.c:2303
#6 0x0000000000609d1c in core_region_nop (listener=0xac5e60, section=
0x7fffffffd6a0) at /work/armbru/qemu/exec.c:3183
#7 0x0000000000667a58 in address_space_update_topology_pass (as=0x12fdca0,
old_view=..., new_view=..., adding=true) at /work/armbru/qemu/memory.c:693
#8 0x0000000000668045 in address_space_update_topology (as=0x12fdca0)
at /work/armbru/qemu/memory.c:722
#9 0x0000000000668147 in memory_region_update_topology (mr=0x0)
at /work/armbru/qemu/memory.c:743
#10 0x0000000000668252 in memory_region_transaction_commit ()
at /work/armbru/qemu/memory.c:764
#11 0x0000000000636612 in i440fx_update_memory_mappings (d=0x13a9310)
at /work/armbru/qemu/hw/i386/../piix_pci.c:155
#12 0x0000000000636db6 in i440fx_common_init (device_name=0x7ea470 "i440FX",
pi440fx_state=0x7fffffffdb98, piix3_devfn=0x7fffffffdb88, isa_bus=
0x7fffffffdb90, pic=0x13a49c0, address_space_mem=0x1381150,
address_space_io=0x1381220, ram_size=0, pci_hole_start=838860,
pci_hole_size=4294128436, pci_hole64_start=4294967296, pci_hole64_size=
4611686018427387904, pci_address_space=0x13a4200, ram_memory=0x13a42b0)
at /work/armbru/qemu/hw/i386/../piix_pci.c:330
#13 0x0000000000636ea8 in i440fx_init (pi440fx_state=0x7fffffffdb98,
piix3_devfn=0x7fffffffdb88, isa_bus=0x7fffffffdb90, pic=0x13a49c0,
address_space_mem=0x1381150, address_space_io=0x1381220, ram_size=838860,
pci_hole_start=838860, pci_hole_size=4294128436, pci_hole64_start=
4294967296, pci_hole64_size=4611686018427387904, pci_memory=0x13a4200,
ram_memory=0x13a42b0) at /work/armbru/qemu/hw/i386/../piix_pci.c:349
#14 0x000000000063469b in pc_init1 (system_memory=0x1381150, system_io=
0x1381220, ram_size=838860, boot_device=0x7fffffffdee0 "cad",
kernel_filename=0x0, kernel_cmdline=0x7cad82 "", initrd_filename=0x0,
cpu_model=0x0, pci_enabled=1, kvmclock_enabled=1)
at /work/armbru/qemu/hw/i386/../pc_piix.c:193
#15 0x0000000000634c0e in pc_init_pci (ram_size=838860, boot_device=
0x7fffffffdee0 "cad", kernel_filename=0x0, kernel_cmdline=0x7cad82 "",
initrd_filename=0x0, cpu_model=0x0)
at /work/armbru/qemu/hw/i386/../pc_piix.c:297
#16 0x000000000057a89e in main (argc=10, argv=0x7fffffffe118, envp=
0x7fffffffe170) at /work/armbru/qemu/vl.c:3520
(gdb) up 4
#4 0x00000000006078fa in register_subpage (section=0x7fffffffd4e0)
at /work/armbru/qemu/exec.c:2263
2263 assert(existing->mr->subpage || existing->mr == &io_mem_unassigned);
(gdb) p/x *section
$1 = {mr = 0x1399860, address_space = 0x1381150, offset_within_region =
0xcccc, size = 0x334, offset_within_address_space = 0xccccc, readonly =
0x0}
