Re: [Qemu-devel] [PATCH 6/6] kvm: Fix dirty tracking with large kernel page size

[Alexander Graf]

On 04.03.2012, at 17:46, Andreas Färber <address@hidden> wrote:

> Am 04.03.2012 12:53, schrieb Benjamin Herrenschmidt:
>> On Sun, 2012-03-04 at 12:49 +0200, Avi Kivity wrote:
>>> On 02/28/2012 11:48 PM, Benjamin Herrenschmidt wrote:
>>>> On Tue, 2012-02-28 at 14:32 +0200, Avi Kivity wrote:
>>>> 
>>>>> What if TARGET_PAGE_SIZE > getpagesize()?  Or is that impossible?
>>>> 
>>>> We have yet to encounter such a case. It's not currently possible on
>>>> power (some old embedded chips could do 1K and 2K page sizes in the TLB
>>>> iirc but we never supported that in Linux and it's being phased out in
>>>> HW).
>>>> 
>>>> I suggest that gets dealt with when/if it needs to, which means probably
>>>> never :-)
>>> 
>>> Doesn't ppc support both 4k and 64k pages?  Suppose you run a 4k guest
>>> on a 64k host?
>>> 
>>> Maybe I'm misremembering or misunderstanding something.
> 
>> TARGET_PAGE_SIZE in qemu is always 4k for powerpc, it's a compile time
>> #define.
> 
> Except for ppcemb-softmmu (1k), which is irrelevant for KVM AFAIU.
> 
> Maybe just add an assert and be done with it?

Assert for what? Linux page size of 64k is something perfectly normal on ppc. 
The hardware can always do at least 4k maps however.

Alex

> 
> For the record, I am hoping to get rid of some of those cpu.h defines in
> a later stage of QOM'ification.
> 
> Andreas
> 
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