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Re: [Qemu-devel] qemu-system-* using mmap?

From: Joseph Miller
Subject: Re: [Qemu-devel] qemu-system-* using mmap?
Date: Wed, 13 Dec 2006 11:04:40 -0500
User-agent: Thunderbird (X11/20060927)

Tim Olson wrote:
I am using qemu 0.8.2 built from source. In the qemu technical documentation for features under full system emulation, it says:

"QEMU can either use a full software MMU for maximum portability or use the host system call mmap() to simulate the target MMU."

However, I cannot find a way to build a full system simulator which does not define SOFTMMU -- in fact, the configure parameters "--disable-system" and "--enable-system" directly control the softmmu switch. There are some mmap() calls in the kqemu code, but to use that requires full kqemu support code in the kernel.

I think there is a big performance hit using the software mmu, as each target load or store instruction is expanded into 20-30 host instructions to perform the translation. Is there a way to build the qemu-system-* emulators using the mmap() feature mentioned in the documentation?

    -- Tim Olson

Qemu-devel mailing list

Can someone elaborate on this a little? What is the difference between the SOFTMMU and the mmap()? Should I be using the --enable-system or the --disable-system for win32 guest on i386 debian host? Can someone give a little more insight on this technicality?


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