mirror of https://github.com/xemu-project/xemu.git
625b370c45
When trying to migrate a machine type pc-q35-6.0 or lower, with this
cmdline options,
-device driver=pcie-root-port,port=18,chassis=19,id=pcie-root-port18,bus=pcie.0,addr=0x12 \
-device driver=nec-usb-xhci,p2=4,p3=4,id=nex-usb-xhci0,bus=pcie-root-port18,addr=0x12.0x1
the following bug happens after all ram pages were sent:
qemu-kvm: get_pci_config_device: Bad config data: i=0x6e read: 0 device: 40 cmask: ff wmask: 0 w1cmask:19
qemu-kvm: Failed to load PCIDevice:config
qemu-kvm: Failed to load pcie-root-port:parent_obj.parent_obj.parent_obj
qemu-kvm: error while loading state for instance 0x0 of device '0000:00:12.0/pcie-root-port'
qemu-kvm: load of migration failed: Invalid argument
This happens on pc-q35-6.0 or lower because of:
{ "ICH9-LPC", ACPI_PM_PROP_ACPI_PCIHP_BRIDGE, "off" }
In this scenario, hotplug_handler_plug() calls pcie_cap_slot_plug_cb(),
which sets dev->config byte 0x6e with bit PCI_EXP_SLTSTA_PDS to signal PCI
hotplug for the guest. After a while the guest will deal with this hotplug
and qemu will clear the above bit.
Then, during migration, get_pci_config_device() will compare the
configs of both the freshly created device and the one that is being
received via migration, which will differ due to the PCI_EXP_SLTSTA_PDS bit
and cause the bug to reproduce.
To avoid this fake incompatibility, there are tree fields in PCIDevice that
can help:
- wmask: Used to implement R/W bytes, and
- w1cmask: Used to implement RW1C(Write 1 to Clear) bytes
- cmask: Used to enable config checks on load.
According to PCI Express® Base Specification Revision 5.0 Version 1.0,
table 7-27 (Slot Status Register) bit 6, the "Presence Detect State" is
listed as RO (read-only), so it only makes sense to make use of the cmask
field.
So, clear PCI_EXP_SLTSTA_PDS bit on cmask, so the fake incompatibility on
get_pci_config_device() does not abort the migration.
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2215819
Signed-off-by: Leonardo Bras <leobras@redhat.com>
Message-Id: <20230706045546.593605-3-leobras@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
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| 9pfs | ||
| acpi | ||
| adc | ||
| alpha | ||
| arm | ||
| audio | ||
| avr | ||
| block | ||
| char | ||
| core | ||
| cpu | ||
| cris | ||
| cxl | ||
| display | ||
| dma | ||
| gpio | ||
| hppa | ||
| hyperv | ||
| i2c | ||
| i386 | ||
| ide | ||
| input | ||
| intc | ||
| ipack | ||
| ipmi | ||
| isa | ||
| loongarch | ||
| m68k | ||
| mem | ||
| microblaze | ||
| mips | ||
| misc | ||
| net | ||
| nios2 | ||
| nubus | ||
| nvme | ||
| nvram | ||
| openrisc | ||
| pci | ||
| pci-bridge | ||
| pci-host | ||
| pcmcia | ||
| ppc | ||
| rdma | ||
| remote | ||
| riscv | ||
| rtc | ||
| rx | ||
| s390x | ||
| scsi | ||
| sd | ||
| sensor | ||
| sh4 | ||
| smbios | ||
| sparc | ||
| sparc64 | ||
| ssi | ||
| timer | ||
| tpm | ||
| tricore | ||
| usb | ||
| vfio | ||
| virtio | ||
| watchdog | ||
| xen | ||
| xenpv | ||
| xtensa | ||
| Kconfig | ||
| meson.build | ||