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[Qemu-devel] Re: [PATCH 4/5] kvmppc: Translate eaddr for fsl_booke mmu

From: Alexander Graf
Subject: [Qemu-devel] Re: [PATCH 4/5] kvmppc: Translate eaddr for fsl_booke mmu
Date: Sat, 29 Aug 2009 23:48:30 +0200

On 24.08.2009, at 19:33, Hollis Blanchard wrote:

On Mon, 2009-08-24 at 10:44 +0800, Liu Yu-B13201 wrote:

IMHO userspace should do the translation and do an ioctl to
fetch the
required information (soft TLB cache / SLB / SDR1) so we can
reuse the
existing qemu infrastructure.

BOOK3S has mmu implement in qemu, but BOOKE doesn't.

Even if it did, I'd be skeptical. But you're right that that's a
critical point: as things stand today, only KVM (not qemu) emulates the
Book E MMU.

Well, that's the whole point I was trying to make.

If we had the booke mmu implemented in qemu debugging would be a lot easier I guess. Also it'd benefit people who for whatever reason want to emulate a booke cpu instead of virtualizing one, maybe because their development machines are x86 ;-).

If I remember the x86 KVM architecture correctly, CR3 (the register holding a phys addr to the current pagetable) gets pulled by userspace and then qemu does the complete translation based on that information.

So yes, we do have two separate MMU implementations for x86 here, but that's a good thing IMHO, because it makes it easier to spot bugs and find out where things went wrong.

So my suggestion is: Implement the BOOKE MMU in Qemu, make an IOCTL to pull the TLB to userspace and thus make life easier for everyone.


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