linux-kernel - Re: Issue with KVM under 4.10 and above

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Date:   Thu, 14 Dec 2017 20:21:46 -0500
From:   Wakko Warner <wakko@...mx.eu.org>
To:     linux-kernel@...r.kernel.org
Subject: Re: Issue with KVM under 4.10 and above

Anyone ?

Wakko Warner wrote:
> Starting with 4.10-rc1, I'm seeing an issue with a VM that boots an old
> kernel.  The VM uses kernel 3.3.0 and is booted directly by qemu.  This VM
> is a copy of a physical machine.
> 
> During boot, it hangs for several seconds on "Using IPI No-Shortcut mode". 
> The next line shows something about ata5 link down.  According to the kernel
> timing, the difference is less than .3 seconds, however many seconds had
> actually passed.  During boot, after fsck finishes, nothing happens, it's
> like it's hung.  When I issue "sleep 1", it takes way longer than 1 second
> to complete.
> 
> I made a copy of another system that has an old kernel (2.6.36.2).  It
> boots, but it hangs for a few seconds after TCP cubic registered then prints
> ata4 link down.  Issueing "sleep 1" takes a long time.  I also noticed that
> issueing date several times shows the same date each time, even several
> minutes later.
> 
> This worked with 4.9.65 and 67 (and older).
> 
> If I change the qemu command line to not use KVM, it works fine, although
> it runs slower.
> 
> I tested some other VMs that use newer kernels (like 4.4.4).  They work OK.
> with the host being 4.10.  I tested linuxmint 18.1 without problems. 
> Issueing date several times shows the time incrementing as expected.

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