Re: [Qemu-devel] Anyone seeing huge slowdown launching qemu with Linux 2.6.35?

[Alexander Graf]

On 04.08.2010, at 19:26, Anthony Liguori wrote:

> On 08/04/2010 11:45 AM, Alexander Graf wrote:
>> Frankly, I partially agreed to your point when we were talking about 300ms 
>> vs. 2 seconds. Now that we're talking 8 seconds that whole point is moot. We 
>> chose the wrong interface to transfer kernel+initrd data into the guest.
>> 
>> Now the question is how to fix that. I would veto against anything normally 
>> guest-OS-visible. By occupying the floppy, you lose a floppy drive in the 
>> guest. By occupying a disk, you see an unwanted disk in the guest.
> 
> 
> Introduce a new virtio device type (say, id 6).  Teach SeaBIOS that 6 is 
> exactly like virtio-blk (id 2).  Make it clear that id 6 is only to be used 
> by firmware and that normal guest drivers should not be written for id 6.

Why not make id 6 be a fw_cfg virtio interface? That way we'd stay 100% 
compatible to everything we have and also get a fast path for reading big 
chunks of data from fw_cfg. All we'd need is a command to set the 'file' we're 
in.

Even better yet, why not use virtio-9p and expose all of fw_cfg as files? Then 
implement a simple virtio-9p client in SeaBIOS and maybe even get direct 
kernel/initrd boot from a real 9p system ;).


Alex