linux-kernel - Re: [PATCH 1/4] KVM: PPC: Add support for multiple-TCE hcalls

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Date:	Mon, 17 Jun 2013 10:42:18 +0200
From:	Alexander Graf <agraf@...e.de>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Alexey Kardashevskiy <aik@...abs.ru>,
	linuxppc-dev@...ts.ozlabs.org,
	David Gibson <david@...son.dropbear.id.au>,
	Paul Mackerras <paulus@...ba.org>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, kvm-ppc@...r.kernel.org
Subject: Re: [PATCH 1/4] KVM: PPC: Add support for multiple-TCE hcalls


On 17.06.2013, at 10:37, Benjamin Herrenschmidt wrote:

> On Mon, 2013-06-17 at 17:55 +1000, Alexey Kardashevskiy wrote:
>> David:
>> ===
>> So, in the case of MULTITCE, that's not quite right.  PR KVM can
>> emulate a PAPR system on a BookE machine, and there's no reason not to
>> allow TCE acceleration as well.  We can't make it dependent on PAPR
>> mode being selected, because that's enabled per-vcpu, whereas these
>> capabilities are queried on the VM before the vcpus are created.
>> ===
>> 
>> Wrong?
> 
> The capability just tells qemu the kernel supports it, it doesn't have
> to depend on PAPR mode, qemu can sort things out no ?

Yes, this goes hand-in-hand with the documentation bit I'm trying to get through to Alexey atm. The CAP merely says that if in PAPR mode the kernel can handle hypercalls X and Y itself.

This is true for all book3s implementations as the patches stand. It is not true for BookE as the patches stand. Hence the CAP should be limited to book3s, regardless of its mode :).


Alex

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