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From: Paul Brook <paul@codesourcery.com>
To: qemu-devel@nongnu.org
Cc: xen-devel@lists.xensource.com, Ian Jackson <Ian.Jackson@eu.citrix.com>
Subject: Re: [Qemu-devel] xen / qemu convergence ?
Date: Mon, 17 Dec 2007 18:55:24 +0000	[thread overview]
Message-ID: <200712171855.25639.paul@codesourcery.com> (raw)
In-Reply-To: <18278.48926.479346.164587@mariner.uk.xensource.com>

> I don't really understand why the vga is handled in this way in qemu
> but then I'm not an expert on PC graphics hardware.  Is it necessary
> or desirable for the VGA RAM to take up virtual address space in this
> way, or is there some other reason why VGA RAM in the ordinary vga
> driver is regarded as a special use of system RAM rather than as a
> special kind of hardware device ?

RAM is RAM. We don't care whether it's nominally owned by the vga controller 
or the "system". If you don't do this then all accesses have to go via 
horribly slow IO callbacks, which is just silly.

I've no idea what you're talking about when you say it's "taking up virtual 
address space".

Paul

WARNING: multiple messages have this Message-ID (diff)
From: Paul Brook <paul@codesourcery.com>
To: qemu-devel@nongnu.org
Cc: xen-devel@lists.xensource.com, Ian Jackson <Ian.Jackson@eu.citrix.com>
Subject: Re: xen / qemu convergence ?
Date: Mon, 17 Dec 2007 18:55:24 +0000	[thread overview]
Message-ID: <200712171855.25639.paul@codesourcery.com> (raw)
In-Reply-To: <18278.48926.479346.164587@mariner.uk.xensource.com>

> I don't really understand why the vga is handled in this way in qemu
> but then I'm not an expert on PC graphics hardware.  Is it necessary
> or desirable for the VGA RAM to take up virtual address space in this
> way, or is there some other reason why VGA RAM in the ordinary vga
> driver is regarded as a special use of system RAM rather than as a
> special kind of hardware device ?

RAM is RAM. We don't care whether it's nominally owned by the vga controller 
or the "system". If you don't do this then all accesses have to go via 
horribly slow IO callbacks, which is just silly.

I've no idea what you're talking about when you say it's "taking up virtual 
address space".

Paul

  parent reply	other threads:[~2007-12-17 18:55 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-12-10 18:14 [Qemu-devel] [PATCH] ioemu/qemu vga: save and restore vram buffer Ian Jackson
2007-12-10 18:14 ` Ian Jackson
2007-12-10 19:03 ` [Qemu-devel] " andrzej zaborowski
2007-12-10 19:03   ` andrzej zaborowski
2007-12-12 11:44   ` [Qemu-devel] [PATCH] ioemu/qemu vga: save and restore vram buffer (revised) Ian Jackson
2007-12-12 11:44     ` Ian Jackson
2007-12-16 11:35     ` [Qemu-devel] " andrzej zaborowski
2007-12-16 11:35       ` andrzej zaborowski
2007-12-17 11:18       ` [Qemu-devel] " Ian Jackson
     [not found]         ` <m2n.s.1JFvsr-002RPK@chiark.greenend.org.uk>
2007-12-17 16:22         ` Paul Brook
2007-12-17 16:22           ` Paul Brook
2007-12-17 18:25           ` [Qemu-devel] xen / qemu convergence ? Ian Jackson
2007-12-17 18:52             ` andrzej zaborowski
2007-12-17 18:52               ` andrzej zaborowski
2007-12-18 10:41               ` [Qemu-devel] " Ian Jackson
2007-12-17 18:55             ` Paul Brook [this message]
2007-12-17 18:55               ` Paul Brook
     [not found]     ` <m2n.s.1JFvre-002RW5@chiark.greenend.org.uk>
2008-01-21 11:41       ` Re: [Qemu-devel] [PATCH] ioemu/qemu vga: save and restore vram buffer (revised) Ian Jackson

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