[Bug 1394326] [NEW] unmapping of persistent grants in qemu

[Xing Lin]

Public bug reported:

A patch was discussed in xen-devel mailing list, to deal with unmapping
of persistent grants in qemu for Xen on 12 Nov 2014. This patch is not
included in any stable qemu release (including 2.0.2, 2.1.2 and
2.2.0-rc2 ) yet. Without this patch, when creating a xen guest from
OpenStack, using the Xen+libvirt approach, it will result in dom0 kernel
crashes, with dmesg as following.

[ 9443.130600] blkfront: xvda: flush diskcache: enabled; persistent grants: enabled; indirect descriptors: disabled;
[ 9443.132818]  xvda: xvda1
[ 9444.604489] xen:grant_table: WARNING: g.e. 0x30 still in use!
[ 9444.604496] deferring g.e. 0x30 (pfn 0xffffffffffffffff)
[ 9444.604499] xen:grant_table: WARNING: g.e. 0x31 still in use!
[ 9444.604502] deferring g.e. 0x31 (pfn 0xffffffffffffffff)
[ 9444.604505] xen:grant_table: WARNING: g.e. 0x32 still in use!
[ 9444.604508] deferring g.e. 0x32 (pfn 0xffffffffffffffff)
  ==== lots of them====
[ 9444.604719] xen:grant_table: WARNING: g.e. 0xe still in use!
[ 9444.604721] deferring g.e. 0xe (pfn 0xffffffffffffffff)
[ 9444.604723] xen:grant_table: WARNING: g.e. 0xd still in use!
[ 9444.604725] deferring g.e. 0xd (pfn 0xffffffffffffffff)
[ 9448.325408] ------------[ cut here ]------------
[ 9448.325421] WARNING: CPU: 5 PID: 19902 at /build/buildd/linux-3.13.0/arch/x86/xen/multicalls.c:129 xen_mc_flush+0x
1a9/0x1b0()
[ 9448.325492] CPU: 5 PID: 19902 Comm: sudo Tainted: GF          O 3.13.0-33-generic #58-Ubuntu
[ 9448.325494] Hardware name: Dell Inc. PowerEdge R710/00W9X3, BIOS 2.1.15 09/02/2010
[ 9448.325497]  0000000000000009 ffff8802d13d9aa8 ffffffff8171bd04 0000000000000000
[ 9448.325501]  ffff8802d13d9ae0 ffffffff810676cd 0000000000000000 0000000000000001
[ 9448.325505]  ffff88030418ffe0 ffff88031d6ab180 0000000000000010 ffff8802d13d9af0
[ 9448.325509] Call Trace:
[ 9448.325518]  [<ffffffff8171bd04>] dump_stack+0x45/0x56
[ 9448.325523]  [<ffffffff810676cd>] warn_slowpath_common+0x7d/0xa0
[ 9448.325526]  [<ffffffff810677aa>] warn_slowpath_null+0x1a/0x20
[ 9448.325530]  [<ffffffff81004e99>] xen_mc_flush+0x1a9/0x1b0
[ 9448.325534]  [<ffffffff81006b99>] xen_set_pud_hyper+0x109/0x110
[ 9448.325538]  [<ffffffff81006c3b>] xen_set_pud+0x9b/0xb0
[ 9448.325543]  [<ffffffff81177f06>] __pmd_alloc+0xd6/0x110
[ 9448.325548]  [<ffffffff81182218>] move_page_tables+0x678/0x720
[ 9448.325552]  [<ffffffff8117ddb7>] ? vma_adjust+0x337/0x7d0
[ 9448.325557]  [<ffffffff811c23fd>] shift_arg_pages+0xbd/0x1b0
[ 9448.325560]  [<ffffffff81181671>] ? mprotect_fixup+0x151/0x290
[ 9448.325564]  [<ffffffff811c26cb>] setup_arg_pages+0x1db/0x200
[ 9448.325570]  [<ffffffff81213edc>] load_elf_binary+0x41c/0xd80
[ 9448.325576]  [<ffffffff8131d503>] ? ima_get_action+0x23/0x30
[ 9448.325579]  [<ffffffff8131c7e2>] ? process_measurement+0x82/0x2c0
[ 9448.325584]  [<ffffffff811c2f7f>] search_binary_handler+0x8f/0x1b0
[ 9448.325587]  [<ffffffff811c44f7>] do_execve_common.isra.22+0x5a7/0x7e0
[ 9448.325591]  [<ffffffff811c49c6>] SyS_execve+0x36/0x50
[ 9448.325596]  [<ffffffff8172cc99>] stub_execve+0x69/0xa0
[ 9448.325599] ---[ end trace 53ac16782e751c0a ]---
[ 9448.347994] ------------[ cut here ]------------
[ 9448.348004] WARNING: CPU: 1 PID: 19902 at /build/buildd/linux-3.13.0/mm/mmap.c:2736 exit_mmap+0x16b/0x170()

** Affects: qemu (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1394326

Title:
  unmapping of persistent grants in qemu

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