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Re: [Qemu-devel] [PATCH, RFC] Update qemu-tech.texi, needs verification
From: |
Blue Swirl |
Subject: |
Re: [Qemu-devel] [PATCH, RFC] Update qemu-tech.texi, needs verification |
Date: |
Mon, 6 Oct 2008 20:53:12 +0300 |
On 10/6/08, Paul Brook <address@hidden> wrote:
> > address@hidden QEMU can either use a full software MMU for maximum
> > portability or
> > use the host system call mmap() to simulate the target MMU. address@hidden
> > +QEMU can either use a full software MMU for maximum portability or use
> > +an in-kernel accelerator (kqemu) to simulate the target MMU.
>
> Referring to kqemu as a MMU simulator is at best very misleading. The item
> you
> removed was referring to qemu-fast, which (in principle at least) still
> worked for cross emulation.
>
> kqemu and kvm execute [some of] the guest code natively, while continuing to
> emulate the rest of the machine.
>
> > Various
> > +hardware devices can be emulated and in some cases, host devices
> > +(e.g. serial and parallel ports, USB, drives) can be used
> > +transparently by the guest Operating System for maximum performance.
>
> This should be a seaprate item. As written it's unclear whether this is a
> kqemu feature or available all the time.
>
> Host device passthrough is generally used for talking to external physical
> peripherals (e.g. a webcam, modem or tape drive), and not for performance
> reasons.
>
>
> > the condition codes are not needed by the next instructions, no
> > condition codes are computed at all.
> >
> > +This optimization is not yet implemented on other targets.
>
>
> I don't think this back propagation pass exists at all now. It was made
> redundant by the TCG liveness pass.
>
> The lazy condition code evaluation is used on x86, m68k and cris. ARM uses a
> simplified variant for the N and Z flags.
>
> You might consider rewording the initial paragraph to say that lazy flag
> evaluation is important for CPUs where every instruction sets the condition
> codes. It tends to be less important on conventional RISC systems where
> condition codes are only updated when explicitly requested.
Okay, I updated the patch based on these comments.
I also added some words about SMP and condition codes and a new
chapter for device emulation.
update_qemu_tech.diff
Description: plain/text
- [Qemu-devel] [PATCH, RFC] Update qemu-tech.texi, needs verification, Blue Swirl, 2008/10/05
- Re: [Qemu-devel] [PATCH, RFC] Update qemu-tech.texi, needs verification, Edgar E. Iglesias, 2008/10/05
- Re: [Qemu-devel] [PATCH, RFC] Update qemu-tech.texi, needs verification, malc, 2008/10/05
- Re: [Qemu-devel] [PATCH, RFC] Update qemu-tech.texi, needs verification, Paul Brook, 2008/10/06
- Re: [Qemu-devel] [PATCH, RFC] Update qemu-tech.texi, needs verification,
Blue Swirl <=
- Re: [Qemu-devel] [PATCH, RFC] Update qemu-tech.texi, needs verification, Paul Brook, 2008/10/06
- Re: [Qemu-devel] [PATCH, RFC] Update qemu-tech.texi, needs verification, Laurent Desnogues, 2008/10/06
- Re: [Qemu-devel] [PATCH, RFC] Update qemu-tech.texi, needs verification, andrzej zaborowski, 2008/10/06
- Re: [Qemu-devel] [PATCH, RFC] Update qemu-tech.texi, needs verification, Kirill A. Shutemov, 2008/10/10