Bug 1724008

Backtrace:

(gdb) bt
#0  0x00007f1ffe9c18af in raise () at /lib64/libc.so.6
#1  0x00007f1ffe9abcc5 in abort () at /lib64/libc.so.6
#2  0x00007f1ffe9abb99 in _nl_load_domain.cold.0 () at /lib64/libc.so.6
#3  0x00007f1ffe9b9e66 in .annobin_assert.c_end () at /lib64/libc.so.6
#4  0x0000562944139a0e in memory_region_get_ram_ptr ()
#5  0x000056294423a0bc in host_memory_backend_memory_complete ()
#6  0x000056294436669f in user_creatable_add_type ()
#7  0x000056294436686a in user_creatable_add_opts ()
#8  0x00005629443669e1 in user_creatable_add_opts_foreach ()
#9  0x00005629444419c2 in qemu_opts_foreach ()
#10 0x00005629440d9cf3 in main ()

Full backtrace:
(gdb) bt full
#0  0x00007f1ffe9c18af in raise () at /lib64/libc.so.6
#1  0x00007f1ffe9abcc5 in abort () at /lib64/libc.so.6
#2  0x00007f1ffe9abb99 in _nl_load_domain.cold.0 () at /lib64/libc.so.6
#3  0x00007f1ffe9b9e66 in .annobin_assert.c_end () at /lib64/libc.so.6
#4  0x0000562944139a0e in memory_region_get_ram_ptr (mr=<optimized out>, mr@entry=0x56294635a060)
    at /usr/src/debug/qemu-kvm-4.0.0-4.module+el8.1.0+3356+cda7f1ee.x86_64/memory.c:2155
        ptr = <optimized out>
        offset = <optimized out>
        __PRETTY_FUNCTION__ = "memory_region_get_ram_ptr"
#5  0x000056294423a0bc in host_memory_backend_memory_complete (uc=<optimized out>, errp=0x7ffccd36cb70) at backends/hostmem.c:324
        lastbit = <optimized out>
        maxnode = <optimized out>
        flags = <optimized out>
        backend = 0x56294635a000
        __func__ = "host_memory_backend_memory_complete"
        bc = <optimized out>
        local_err = 0x0
        ptr = <optimized out>
        sz = <optimized out>
#6  0x000056294436669f in user_creatable_add_type
    (type=type@entry=0x56294630b060 "memory-backend-file", id=id@entry=0x56294630b040 "mem0", qdict=qdict@entry=0x5629463999d0, v=v@entry=0x56294639a9f0, errp=errp@entry=0x562944cb7b10 <error_fatal>) at qom/object_interfaces.c:86
        obj = 0x56294635a000
        klass = <optimized out>
        e = <optimized out>
        local_err = 0x0
        __func__ = "user_creatable_add_type"
        __PRETTY_FUNCTION__ = "user_creatable_add_type"
#7  0x000056294436686a in user_creatable_add_opts (opts=opts@entry=0x56294630aff0, errp=errp@entry=0x562944cb7b10 <error_fatal>)
    at qom/object_interfaces.c:127
        v = 0x56294639a9f0
        pdict = 0x5629463999d0
        obj = <optimized out>
        id = 0x56294630b040 "mem0"
        type = 0x56294630b060 "memory-backend-file"
        __func__ = "user_creatable_add_opts"
#8  0x00005629443669e1 in user_creatable_add_opts_foreach
    (opaque=0x562944224ce0 <object_create_delayed>, opts=0x56294630aff0, errp=0x562944cb7b10 <error_fatal>)
    at qom/object_interfaces.c:150
        type_opt_predicate = 0x562944224ce0 <object_create_delayed>
        obj = 0x0
        type = <optimized out>
#9  0x00005629444419c2 in qemu_opts_foreach
    (list=<optimized out>, func=0x5629443669a0 <user_creatable_add_opts_foreach>, opaque=0x562944224ce0 <object_create_delayed>, errp=0x562944cb7b10 <error_fatal>) at util/qemu-option.c:1171
        loc = {kind = LOC_CMDLINE, num = 2, ptr = 0x7ffccd36cec0, prev = 0x562944cb7b30 <std_loc>}
        opts = 0x56294630aff0
        rc = 0
        __PRETTY_FUNCTION__ = "qemu_opts_foreach"
#10 0x00005629440d9cf3 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at vl.c:4442
        i = <optimized out>
        snapshot = 0
        linux_boot = <optimized out>
        initrd_filename = 0x0
        kernel_filename = 0x0
        kernel_cmdline = <optimized out>
        boot_order = 0x5629444eade0 "cad"
        boot_once = <optimized out>
        ds = <optimized out>
        opts = <optimized out>
        machine_opts = <optimized out>
        icount_opts = 0x0
        accel_opts = 0x0
        olist = <optimized out>
        optind = 3
        optarg = 0x7ffccd36d4a7 "memory-backend-file,id=mem0,mem-path=/dev/pmem4,size=1G,share,pmem=on"
        loadvm = 0x0
        machine_class = 0x562946341760
        cpu_model = 0x0
        vga_model = 0x0
        qtest_chrdev = 0x0
        qtest_log = 0x0
        incoming = 0x0
        userconfig = <optimized out>
        nographic = false
        display_remote = <optimized out>
        log_mask = <optimized out>
        log_file = <optimized out>
        trace_file = <optimized out>
        maxram_size = <optimized out>
        ram_slots = <optimized out>
        vmstate_dump_file = 0x0
        main_loop_err = 0x0
        err = 0x0
        list_data_dirs = <optimized out>
        dir = <optimized out>
        bdo_queue = {sqh_first = 0x0, sqh_last = 0x7ffccd36cd50}
        __func__ = "main"

Reproduced with qemu-kvm-4.1.0-1.module+el8.1.0+3966+4a23dca1.

# /usr/libexec/qemu-kvm  -object memory-backend-file,id=mem0,mem-path=/dev/pmem0,size=1G,share,pmem=on
qemu-kvm: /builddir/build/BUILD/qemu-4.1.0-rc4/memory.c:2203: memory_region_get_ram_ptr: Assertion `mr->ram_block' failed.
Aborted (core dumped)

*** Bug 1732683 has been marked as a duplicate of this bug. ***

*** Bug 1732683 has been marked as a duplicate of this bug. ***

I have posted a backport for bz1736788 which also fixed this BZ.  I'm not marking it as a duplicate because the root cause is different and this BZ should still be verified.

Verify:
qemu-kvm-4.1.0-11.module+el8.1.0+4250+4f5fbfdc
kernel-4.18.0-145.el8.x86_64

Same steps as comment 0, generate /dev/pmem0 by modify host kernel line, then boot guest with /dev/pmem0. No core dumped, only got a warning, and guest can boot up normally. 

# /usr/libexec/qemu-kvm -M pc,nvdimm  \
-object memory-backend-file,id=mem0,mem-path=/dev/pmem0,size=4G,share,pmem=on \
-device nvdimm,memdev=mem0,id=nv0 ...
Warning: requesting persistence across crashes for backend file /dev/pmem0 failed. Proceeding without persistence, data might become corrupted in case of host crash.
QEMU 4.1.0 monitor - type 'help' for more information
(qemu) 


Also tried with a real nvdimm device on host, but still got the same warning. Stefan, would you please help confirm if it is expected? Thanks.

Thanks for the update, Pankaj!

Duplicated issue BUG 1732683 still reproduced on RHEL8.1 rc1:
Kernel version: 4.18.0-147.el8.x86_64
Qemu version: 4.1.0 (qemu-kvm-4.1.0-7.module+el8.1.0+4177+896cb282)

(In reply to belinda from comment #16)
> Duplicated issue BUG 1732683 still reproduced on RHEL8.1 rc1:
> Kernel version: 4.18.0-147.el8.x86_64
> Qemu version: 4.1.0 (qemu-kvm-4.1.0-7.module+el8.1.0+4177+896cb282)

Hi Belinda,

This bug is fixed in qemu-kvm-4.1.0-11.module+el8.1.0+4250+4f5fbfdc, please test with fixed version, thanks.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2019:3723