Severe guest disk corruption with device_model_stubdomain_override=1...

[Sarah Newman <srn@prgmr.com>]

And nested xen.

CPU: AMD Opteron 2352
Outer configuration: Xen4CentOS 6 xen 4.6.1-2.el6, linux 3.18.25-18.el6.x86_64
Inner configuration: Xen4CentOS 6 xen 4.6.1-2.el6, linux 3.18.25-19.el6.x86_64
Inner xen command line:  cpuinfo loglvl=all guest_loglvl=error dom0_mem=512M,max:512M com1=115200,8n1 console=com1 dom0_max_vcpus=1 dom0_vcpus_pin=true
Inner linux command line: ro root=LABEL=DISK rootflags=barrier=0 swiotlb=32768 console=hvc0

Relevant parts of xl.cfg:
builder = 'hvm'
memory = 2688
vcpus = 1
pae = 1
nx = 1
acpi = 1
viridian = 0
xen_platform_pci = 0
apic = 1
device_model_stubdomain_override = 1
disk = ['file:/var/lib/instance-disks/c6:0,hda,w',
        'file:/var/lib/instance-disks/c6:1,hdb,w',
        'file:/var/lib/instance-disks/c6:2,hdc,w']

This is the error that typically comes up with device_model_stubdomain_override=1:

scsi host0: ata_piix


scsi host1: ata_piix


ata1: PATA max MWDMA2 cmd 0x1f0 ctl 0x3f6 bmdma 0xc200 irq 14


ata2: PATA max MWDMA2 cmd 0x170 ctl 0x376 bmdma 0xc208 irq 15


ata1.00: ATA-7: QEMU HARDDISK, 0.10.2, max UDMA/100


ata1.00: 20971520 sectors, multi 16: LBA48


ata1.01: ATA-7: QEMU HARDDISK, 0.10.2, max UDMA/100


ata1.01: 209715200 sectors, multi 16: LBA48


ata2.00: ATA-7: QEMU HARDDISK, 0.10.2, max UDMA/100


ata2.00: 41943040 sectors, multi 16: LBA48


ata2.00: configured for MWDMA2


ata1.00: configured for MWDMA2


ata1.01: configured for MWDMA2


scsi 0:0:0:0: Direct-Access     ATA      QEMU HARDDISK    .2   PQ: 0 ANSI: 5


scsi 0:0:1:0: Direct-Access     ATA      QEMU HARDDISK    .2   PQ: 0 ANSI: 5


scsi 1:0:0:0: Direct-Access     ATA      QEMU HARDDISK    .2   PQ: 0 ANSI: 5


sd 0:0:0:0: [sda] 20971520 512-byte logical blocks: (10.7 GB/10.0 GiB)


sd 0:0:1:0: [sdb] 209715200 512-byte logical blocks: (107 GB/100 GiB)


sd 1:0:0:0: [sdc] 41943040 512-byte logical blocks: (21.4 GB/20.0 GiB)


sd 0:0:1:0: [sdb] Write Protect is off


sd 1:0:0:0: [sdc] Write Protect is off


sd 0:0:0:0: [sda] Write Protect is off


sd 0:0:1:0: [sdb] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA


sd 0:0:0:0: [sda] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA


sd 1:0:0:0: [sdc] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA


...
sd 0:0:0:0: [sda] Attached SCSI disk


sd 0:0:1:0: [sdb] Attached SCSI disk


sd 1:0:0:0: [sdc] Attached SCSI disk


....
sd 0:0:0:0: Attached scsi generic sg0 type 0


sd 0:0:1:0: Attached scsi generic sg1 type 0


sd 1:0:0:0: Attached scsi generic sg2 type 0


...

ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0


ata1.00: BMDMA stat 0x4


ata1.00: failed command: READ DMA


ata1.00: cmd c8/00:08:d0:09:a5/00:00:00:00:00/e0 tag 0 dma 4096 in


         res 41/04:08:d0:09:a5/00:00:00:00:00/e0 Emask 0x1 (device error)


ata1.00: status: { DRDY ERR }


ata1.00: error: { ABRT }



Out of curiosity, I tried adding libata.dma=0 to the linux command line and after that, the corruption was bad enough I had to start over.

With the normal command line, device_model_stubdomain_override = 0, and nested xen, there are no errors.
After adding libata.dma=0 to the kernel command line, with device_model_stubdomain_override = 0 and nested xen, there are no errors.

xen_platform_pci seems to be ignored with device_model_stubdomain_override=1. So I don't think I can test what happens with the 3.18.25-19.el6.x86_64
kernel, no nested xen, and non-paravirtual block devices.

--Sarah

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