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Re: [Qemu-devel] How to measure guest memory access (qemu_ld/qemu_st) ti

From: Lluís Vilanova
Subject: Re: [Qemu-devel] How to measure guest memory access (qemu_ld/qemu_st) time?
Date: Mon, 18 Jun 2012 22:38:36 +0300
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1.50 (gnu/linux)

陳韋任 (Wei-Ren Chen) writes:

>> The reason why we want to do the measuring is we want to use KVM (sounds 
>> crazy
>> idea) MMU virtualization to speedup the guest -> host memory address 
>> translation.
>> I talked to some people on LinuxCon Japan, included Paolo, about this idea. 
>> The
>> feedback I got is we can only use shadow page table rather than EPT/NPT to do
>> the address translation (if possible!) since different ISA (ARM and x86, for
>> example) have different page table format. Besides, QEMU has to use ioctl to 
>> ask
>> KVM to get the translation result, but it's an overkill as the ARM page table
>> is quite simple, which can be done in user mode very fast.

>   Anyone would like to give a comment on this? ;)

>   From the talk with Laurent on #qemu, he said the way he thought of is
> translating GVA -> GPA manually (through software), then try to insert
> GPA -> HPA into EPT, that's the only way HW can help.

Sorry, but I don't see the benefit here.


 "And it's much the same thing with knowledge, for whenever you learn
 something new, the whole world becomes that much richer."
 -- The Princess of Pure Reason, as told by Norton Juster in The Phantom

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