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[Qemu-devel] Re: POLL: Why do you use kqemu?
From: |
Jan Kiszka |
Subject: |
[Qemu-devel] Re: POLL: Why do you use kqemu? |
Date: |
Mon, 08 Jun 2009 15:18:46 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
Avi Kivity wrote:
> Jan Kiszka wrote:
>> And the fact that kqemu has to use tcg in order to achieve a reasonable
>> performance is rather a disadvantage. The complexity and overhead for
>> synchronizing tcg with the in-kernel accelerator is enormous. If there
>> were a feasible way to overcome this with kqemu, it would benefit a lot.
>> But unfortunately there is none (given you don't want to invest
>> reasonable efforts).
>>
>
> Note that kvm suffers from something similar (to a smaller magnitude) as
> well: if a guest pages in its page tables, kvm knows nothing about it
> and will thus have outdated shadows. To date we haven't encountered a
> problem with it, but it's conceivable. I think Windows can page its
> page tables, but maybe it's disabled by default, or maybe it doesn't dma
> directly into the page tables.
Can't follow, always thought that kernel space gets informed when some
I/O operation handled by user space modified an "interesting" page.
>
> Not sure how to fix. Maybe write protect the host page tables when we
You mean guest page table?
> shadow a page table, and get an mmu notifier to tell us when its made
> writable? Seems expensive. Burying head in sand is much easier.
>
Does this still apply to nested paging? I guess (hope) not...
Jan
--
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux
- Re: [Qemu-devel] POLL: Why do you use kqemu?, (continued)
- Re: [Qemu-devel] POLL: Why do you use kqemu?, Lennart Sorensen, 2009/06/05
- Re: [Qemu-devel] POLL: Why do you use kqemu?, Johannes Schindelin, 2009/06/05
- Re: [Qemu-devel] POLL: Why do you use kqemu?, Jamie Lokier, 2009/06/07
- Re: [Qemu-devel] POLL: Why do you use kqemu?, Avi Kivity, 2009/06/08
- Re: [Qemu-devel] POLL: Why do you use kqemu?, Jamie Lokier, 2009/06/08
- Re: [Qemu-devel] POLL: Why do you use kqemu?, Avi Kivity, 2009/06/08
- Re: [Qemu-devel] POLL: Why do you use kqemu?, Jamie Lokier, 2009/06/08
- Re: [Qemu-devel] POLL: Why do you use kqemu?, Avi Kivity, 2009/06/08
- [Qemu-devel] Re: POLL: Why do you use kqemu?, Jan Kiszka, 2009/06/08
- [Qemu-devel] Re: POLL: Why do you use kqemu?, Avi Kivity, 2009/06/08
- [Qemu-devel] Re: POLL: Why do you use kqemu?,
Jan Kiszka <=
- [Qemu-devel] Re: POLL: Why do you use kqemu?, Avi Kivity, 2009/06/08
- [Qemu-devel] Re: POLL: Why do you use kqemu?, Jan Kiszka, 2009/06/08
- [Qemu-devel] Re: POLL: Why do you use kqemu?, Avi Kivity, 2009/06/08
- [Qemu-devel] Re: POLL: Why do you use kqemu?, Jan Kiszka, 2009/06/08
- Re: [Qemu-devel] POLL: Why do you use kqemu?, Lennart Sorensen, 2009/06/08
Re: [Qemu-devel] POLL: Why do you use kqemu?, Andreas Färber, 2009/06/06