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Re: [Qemu-devel] [RFC] Host vs Guest memory allocation
From: |
Alexander Graf |
Subject: |
Re: [Qemu-devel] [RFC] Host vs Guest memory allocation |
Date: |
Mon, 12 Apr 2010 17:39:04 +0200 |
On 12.04.2010, at 17:09, Avi Kivity wrote:
> On 04/12/2010 05:55 PM, Richard Henderson wrote:
>>
>>> You could reduce the overhead somewhat by using kvm for memory
>>> translation on hosts that support it. Of course tcg translation and
>>> syscall costs will grow by the exit overhead.
>>
>> I've thought about this a bit, and what seemed to be the stickler is
>> what is the environment that runs in the guest? TCG generated code
>> is of course fine, but what about the helper functions? How can we
>> tell whether a given helper function can run in the restricted environment
>> of the guest or whether it needs to transition back to the environment of
>> the host to do its work?
>
> I'd guess all helpers can run in guest context except those that cause a
> transition to target kernel mode.
>
>> I suppose the obvious solution is some sort of flag on the function that
>> well-maintained ports will set. But the whole marshalling thing is still
>> pretty tricky.
>
> Pass everything through memory; will there be many transitions apart from
> trapping instructions and missing translations?
I don't see how that would help with the 64-on-32 issue. You still don't get a
64 bit address space from running inside KVM.
Alex
- [Qemu-devel] [RFC] Host vs Guest memory allocation, Richard Henderson, 2010/04/05
- Re: [Qemu-devel] [RFC] Host vs Guest memory allocation, Aurelien Jarno, 2010/04/05
- Re: [Qemu-devel] [RFC] Host vs Guest memory allocation, Avi Kivity, 2010/04/12
- Re: [Qemu-devel] [RFC] Host vs Guest memory allocation, Richard Henderson, 2010/04/12
- Re: [Qemu-devel] [RFC] Host vs Guest memory allocation, Avi Kivity, 2010/04/12
- Re: [Qemu-devel] [RFC] Host vs Guest memory allocation,
Alexander Graf <=
- Re: [Qemu-devel] [RFC] Host vs Guest memory allocation, Avi Kivity, 2010/04/12
- Re: [Qemu-devel] [RFC] Host vs Guest memory allocation, Alexander Graf, 2010/04/12
- Re: [Qemu-devel] [RFC] Host vs Guest memory allocation, Avi Kivity, 2010/04/12
Re: [Qemu-devel] [RFC] Host vs Guest memory allocation, Paul Brook, 2010/04/12