Re: [kvm-ppc-devel] [PATCH] [3/4] Add userpace tlb access

[Hollis Blanchard <hollisb@us.ibm.com>]

On Thu, 2008-01-31 at 09:32 +0100, Christian Ehrhardt wrote:
> Hollis Blanchard wrote:
> > 
> > Didn't we agree not to export the shadow TLB?
> 
> The last agreement I found was to export shadow TLB read only which is what I have here.
> But it's easy to remove if needed ;-)
> So do you think it is really completely useless e.g. on a tlb dump ? If yes we can remove it, but
> if it can give us even a small benefit we should keep the read only access.

OK, we can keep it.

We will need custom debug tool code to understand any TLB dump anyways.

> >> +struct kvm_tlbe {
> >> +	__u32 index;
> >> +	union {
> >> +		struct tlbe tlbe_ppc440;
> >> +		/* Fix the size of the union (hopefully) */
> >> +		char padding[32];
> >> +	};
> >> +};
> > 
> > Are you sure 32 bytes will be large enough? I think Freescale uses a ton
> > of MAS registers for TLB insertion.
> 
> Well I thought it should be enough but we can use 64bit just to be safer.

I guess you mean 64 bytes. Wei, how many bytes do you think are needed
to save current and future TLB entries?

-- 
Hollis Blanchard
IBM Linux Technology Center


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