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SubjectRe: [Xen-devel] Xen/cdrom: Ubuntu 16.04 VM read the content from CD-ROM abnormally

On 2016/12/10 0:15, Konrad Rzeszutek Wilk wrote:
> On Fri, Dec 09, 2016 at 04:21:02PM +0800, Ken wrote:
>> Hi all,
>> I run the Ubuntu 16.04 server (2 vcpu/2G, Linux 4.4.0) on the Xen-4.1.2, and
>> installed gcc through the CDROM used by 16.04 iso file, when I installed gcc
>> that depends deb packages to decompress failed. But uploaded the ISO files
>> into the VM are mounted by loop or used as CDROM for other VM (Fedora 24)
>> transport these abnormal files to 16.04 are available. So the 16.04 ISO file
>> should be correct.
>> Then I went to try to fix this problem, the steps are as follows:
>> First of all, I was worried because the Hypervisor version is too old to
>> cause this problems, so I upgraded to the Xen upstream and found that there
>> are the problem still.
>> Then, I went to attempted to upgrade the VM kernel, by dichotomy to find the
>> smallest available kernel, but found that the kernel patch has nothing to do
>> the cdrom or isofs driver, Linux kernel committed history has nothing to do
>> these, combined with the Fedora within Linux 4.4.0 have no problem, so I
>> inferred the kernel had no this defective.
>> The above comparison can not troubleshoot the problem, so I analyzed the
>> Linux CD-ROM device loading process to confirm that the problem is
>> encountered before the mount. and I found the following three strange
>> phenomenon:
>> 1. Using Ubuntu 14.04.5 udevadm, re-packaged the init-ramfs of 16.04, reboot
>> the VM, read the content of CD-ROM successfully, but compile the system-204
>> from the 14.04.5 and installed on 16.04, the problem still can not be
>> resolved, some abnormal logs as blow:
>> random: udevadm: uninitialized urandom read (16 bytes read, 28 bits of
>> entropy available)
>> 2. found that the VM registers dmi failed at startup, so I removed the dmi
>> driver, reboot the VM, read the content of CD-ROM successfully, and from the
>> kernel dmi_scan_machine code, it should not affect to use the CD-ROM, The
>> failed logs as blow:
>> ioremap error for 0xfc001000-0xfc002000, requested 0x2, got 0x0
>> dmi: Firmware registration failed.
>> 3. Deploy the VM within 8 vcpus, 8G memory, read the content of CD-ROM
>> successfully.
>> Therefore, I inferred this anomaly that has several problems, but can not
>> focus it, there are other people have encountered this same anomaly? Do
>> anyone have any suggests to
>> debug it next step?
> I think you are the first one to see this. I had run small guests before
> (1GB, 1VCPU) with ISO and did not encounter these issues. Are there
> erorrs in the dmesg when the file is copied?

The other VM are normal, it is only with Ubuntu 16.04 and its
LTS(smaller than 8GB, 8VCPU). sometimes, the ubuntu 16.04 encountered
problem that maybe printed some logs as blow:
ISOFS: Interleaved files not (yet) supported.
ISOFS: inode->i_ino = (14976).
ISOFS: File unit size != 0 for ISO file (14976).

>> Thanks.
>> _______________________________________________
>> Xen-devel mailing list
> .

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