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

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Message-ID: <20161209161543.GB11877@char.us.oracle.com>
Date:   Fri, 9 Dec 2016 11:15:43 -0500
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Ken <jinjian@...wei.com>
Cc:     xen-devel@...ts.xenproject.org, axboe@...e.de, rth@...ddle.net,
        linux-kernel@...r.kernel.org, xuquan8@...wei.com,
        zhang.zhanghailiang@...wei.com, pss.wulizhen@...wei.com
Subject: Re: [Xen-devel] Xen/cdrom: Ubuntu 16.04 VM read the content from
 CD-ROM abnormally

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?
> 
> Thanks.
> 
> 
> 
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