On 07/04/2018 04:26 AM, Peter Xu wrote: > On Tue, Jul 03, 2018 at 02:45:24PM +0200, Cédric Le Goater wrote: >> On 07/02/2018 05:57 AM, Peter Xu wrote: >>> On Sun, Jul 01, 2018 at 07:19:53PM +0200, Cédric Le Goater wrote: >>>> When a PCI device is unplugged, the PCI memory regions are deleted >>>> before the optional ROM RAMBlock is flagged non-migratable. But, when >>>> this is done, the RAMBlock has already been cleared from the region, >>>> leading to a segv. >>>> >>>> Fix the issue by testing the RAMBlock before flagging it, as it is >>>> done in qemu_ram_unset_idstr() >>>> >>>> Signed-off-by: Cédric Le Goater <c...@kaod.org> >>>> --- >>>> >>>> I caught this bug while deleting a passthrough device from a pseries >>>> machine. Here is the stack: >>>> >>>> #0 qemu_ram_unset_migratable (rb=0x0) at >>>> /home/legoater/work/qemu/qemu-xive-3.0.git/exec.c:1994 >>>> #1 0x000000010072def0 in vmstate_unregister_ram (mr=0x101796af0, >>>> dev=<optimized out>) >>>> #2 0x0000000100694e5c in pci_del_option_rom (pdev=0x101796330) >>>> #3 pci_qdev_unrealize (dev=<optimized out>, errp=<optimized out>) >>>> #4 0x00000001005ff910 in device_set_realized (obj=0x101796330, >>>> value=<optimized out>, errp=0x0) >>>> #5 0x00000001007a487c in property_set_bool (obj=0x101796330, >>>> v=<optimized out>, name=<optimized out>, >>>> #6 0x00000001007a7878 in object_property_set (obj=0x101796330, >>>> v=0x7fff70033110, >>>> #7 0x00000001007aaf1c in object_property_set_qobject (obj=0x101796330, >>>> value=<optimized out>, >>>> #8 0x00000001007a7b90 in object_property_set_bool (obj=0x101796330, >>>> value=<optimized out>, >>>> #9 0x00000001005fcdd8 in device_unparent (obj=0x101796330) >>>> #10 0x00000001007a6dd0 in object_finalize_child_property >>>> (obj=<optimized out>, name=<optimized out>, >>>> #11 0x00000001007a50c0 in object_property_del_child (obj=0x10111f800, >>>> child=0x101796330, >>>> #12 0x0000000100425cc0 in spapr_phb_remove_pci_device_cb >>>> (dev=0x101796330) >>>> #13 0x0000000100427974 in spapr_drc_release (drc=0x1017e2df0) >>>> #14 0x0000000100429098 in spapr_drc_detach (drc=0x1017e2df0) >>>> #15 0x00000001004294e0 in drc_isolate_physical (drc=0x1017e2df0) >>>> #16 0x000000010042a50c in rtas_set_isolation_state (state=0, >>>> idx=<optimized out>) >>>> >>>> May be we should call pci_del_option_rom() before >>>> pci_unregister_io_regions() ? >>> >>> This seems to make more sense to me. >>> >>> Meanwhile I assume the name pci_del_option_rom() is a bit misleading - >>> it's not really deleting the ROM but unregistering the ROM only. >>> Instead IIUC it's pci_unregister_io_regions() which deleted that. So >>> maybe we can either rename the function pci_del_option_rom(), or we >>> can pick the ROM destruction out of pci_unregister_io_regions() and >>> put it into pci_del_option_rom() to make sure it's done as the last >>> step? >> >> So it is a little more complex than I thought. >> >> The PCI device is a vfio PCI device and the PCI ROM region is initialized >> in vfio_pci_size_rom() with memory_region_init_io(), which does not >> allocate the RAMBlock, but has_rom is still set to true. >> >> When the device is deleted, pci_del_option_rom() is called and with it, >> vmstate_unregister_ram() because has_rom is set to true. Leading to the >> SEGV. >> >> I am not sure how to handle this case. It seems that the realize routine >> of VFIOPCIDevice is hijacking a little the PCIDevice layer. > > Indeed. > > Then now I'm a bit confused on who actually deleted the ROM memory > region that was created when pci_add_option_rom() was called. It > seems to be leaked. > > AFAIU the rest of the memory regions of the BARs (0-5) are managed by > specific device emulation code, however this ROM memory region is > managed by PCI subsystem. Not sure whether that means we should > destroy the region in PCI subsystem too, e.g. in pci_del_option_rom(). > > And now I see this patch might be a valid fix for the VFIO-specific > issue (though we might comment that a bit somewhere).
yes. I will send a v2 with an updated commit log. Thanks, C.
