[Qemu-devel] Make -std-vga the default?

[Qemu-devel] Make -std-vga the default?

[Julian Seward]

I've been using -std-vga for a couple of weeks now, and it works well
at least for the guests I've been using (Win2K/XP, Red Hat 9, SuSE 10.1).

Overall it seems to work much better than the default 5446 simulation
and it seems to me that non-developer users, who are presumably the larger 
fraction of the user base, would benefit from having -std-vga as the
default.  The "it just works" property is important for new users, and
-std-vga has more of that than the 5446 just at the moment.

J

Re: [Qemu-devel] Make -std-vga the default?

[Paul Brook]

On Wednesday 28 June 2006 02:21, Julian Seward wrote:
> I've been using -std-vga for a couple of weeks now, and it works well
> at least for the guests I've been using (Win2K/XP, Red Hat 9, SuSE 10.1).

Really? My win2k install couldn't do anything useful with -std-vga. It would 
only do the very basic 640x480x4 mode. I'm fairly sure win9x can't do 
anything useful with straight VGA either.

> Overall it seems to work much better than the default 5446 simulation
> and it seems to me that non-developer users, who are presumably the larger
> fraction of the user base, would benefit from having -std-vga as the
> default.  The "it just works" property is important for new users, and
> -std-vga has more of that than the 5446 just at the moment.

In my experience the Cirrus emulation "just works", and is supported by pretty 
much every OS out the box. AFAIK Windows earlier than XP doesn't needs 
additional 3rd party drivers to support anonymous VESA hardware.

Paul

Re: [Qemu-devel] Make -std-vga the default?

[Kevin F. Quinn]

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On Wed, 28 Jun 2006 06:30:51 +0100
Paul Brook <paul@codesourcery.com> wrote:

> On Wednesday 28 June 2006 02:21, Julian Seward wrote:
> > I've been using -std-vga for a couple of weeks now, and it works
> > well at least for the guests I've been using (Win2K/XP, Red Hat 9,
> > SuSE 10.1).
> 
> Really? My win2k install couldn't do anything useful with -std-vga.
> It would only do the very basic 640x480x4 mode. I'm fairly sure win9x
> can't do anything useful with straight VGA either.

Same here.  Also std-vga seemed to be slower than cirrus when I tried
it recently on my linux guests, although I haven't actually measured
anything.

> > Overall it seems to work much better than the default 5446

Julian, in what way is std-vga better than the cirrus emulation?

> > simulation and it seems to me that non-developer users, who are
> > presumably the larger fraction of the user base, would benefit from
> > having -std-vga as the default.  The "it just works" property is
> > important for new users, and -std-vga has more of that than the
> > 5446 just at the moment.
> 
> In my experience the Cirrus emulation "just works", and is supported
> by pretty much every OS out the box. AFAIK Windows earlier than XP
> doesn't needs additional 3rd party drivers to support anonymous VESA
> hardware.

Seconded - the default should be the one best supported by guests out
of the box.  As it stands, that's cirrus.

> 
> Paul
> 
-- 
Kevin F. Quinn

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Re: [Qemu-devel] Make -std-vga the default?

[Julian Seward]

> > Really? My win2k install couldn't do anything useful with -std-vga.
> > It would only do the very basic 640x480x4 mode. I'm fairly sure win9x
> > can't do anything useful with straight VGA either.
>
> Same here.  Also std-vga seemed to be slower than cirrus when I tried
> it recently on my linux guests, although I haven't actually measured
> anything.

My mistake; Win2K doesn't like -std-vga.  I confused 2K and XP.

> > > Overall it seems to work much better than the default 5446
>
> Julian, in what way is std-vga better than the cirrus emulation?

I can go above 1024x768, which is realistically something I need in
order to use QEMU as a viable replacement for VMware.

With SuSE 10.1 guest I can't even get 1024x768 with Cirrus.  SuSE
claims it's doing 1024x768 but what I get is 1024x600.

> > In my experience the Cirrus emulation "just works", and is supported
> > by pretty much every OS out the box. AFAIK Windows earlier than XP
> > doesn't needs additional 3rd party drivers to support anonymous VESA
> > hardware.

I agree that avoiding additional drivers is good.  However it seems that
both cirrus and std-vga have their shortcomings and neither is an ideal
out-of-the-box solution right now.

J

[Qemu-devel] Qemu developement documentation?

[Tieu Ma Dau]

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Hi all,
  I'm developping Qemu to simulate ARM processor and I also read the file  qemu-tech.html in Qemu source code. But I don't understand very well  the idea that Qemu simulates a (exp: x86) instruction. 
  [quote]
    The basic idea is to split every x86 instruction into fewer simpler  instructions. Each simple instruction is implemented by a piece of C  code (see `target-i386/op.c'). Then a compile time tool  (`dyngen') takes the corresponding object file (`op.o')  to generate a dynamic code generator which concatenates the simple  instructions to build a function (see `op.h:dyngen_code()')
  [/quote]
  (I don't understand the explanation in bold)
  + What does the explanation in bold mean? Or do you have any document which clarifies this?
  + Do you have any document which explains how Qemu works (idea for the working of Qemu)?
  + Does Qemu works (i.e get the instruction from the target OS, splits  the instruction into simpler instructions, executes the instructions on  host OS...) same as the other simulators?
  Best regards
  Tieu
  
 		
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Re: [Qemu-devel] Qemu developement documentation?

[Jonas Maebe]

On 28 jun 2006, at 10:48, Tieu Ma Dau wrote:

> [quote]
> The basic idea is to split every x86 instruction into fewer simpler  
> instructions. Each simple instruction is implemented by a piece of  
> C code (see `target-i386/op.c'). Then a compile time tool  
> (`dyngen') takes the corresponding object file (`op.o') to generate  
> a dynamic code generator which concatenates the simple instructions  
> to build a function (see `op.h:dyngen_code()')
> [/quote]
> (I don't understand the explanation in bold)

Since I'm reading your message in plain text, I don't know what part  
of your quote is bold, but what happens is this:
* a number of basic operations are defined, and each of these basic  
operations is implemented using a C function (so the implementation  
is mostly cpu-independent)
* the functions with these simple operations are put together in  
"op.c", and this file is compiled by a compiler on the host platform  
into op.o
* dyngen more or less disassembles this generated op.o: for each of  
those functions, it gets the assembler code, but strips out entry and  
exit code
* when emulating, for each to be emulated instruction Qemu simply  
copies the appropriate assembler code gotten by dyngen from op.o

By putting all those copied code fragments after each other, the full  
program is emulated. There are some special tricks for things like  
jumps (a special symbol which is found using the relocation  
information, and which then can be replaced during emulation with the  
actual target), but overall that's it.


Jonas

Re: [Qemu-devel] Make -std-vga the default?

[Natalia Portillo]

Hi,

>> I've been using -std-vga for a couple of weeks now, and it works well
>> at least for the guests I've been using (Win2K/XP, Red Hat 9, SuSE  
>> 10.1).
>
> Really? My win2k install couldn't do anything useful with -std-vga.  
> It would
> only do the very basic 640x480x4 mode. I'm fairly sure win9x can't do
> anything useful with straight VGA either.
Same here

>> Overall it seems to work much better than the default 5446 simulation
>> and it seems to me that non-developer users, who are presumably  
>> the larger
>> fraction of the user base, would benefit from having -std-vga as the
>> default.  The "it just works" property is important for new users,  
>> and
>> -std-vga has more of that than the 5446 just at the moment.
>
> In my experience the Cirrus emulation "just works", and is  
> supported by pretty
> much every OS out the box. AFAIK Windows earlier than XP doesn't needs
> additional 3rd party drivers to support anonymous VESA hardware.
That are most of time difficult to find and commercial only.
Not to say for OS/2, Windows 3.x, etc

Regards