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Subject: Re: [PATCH 08/19] KVM: PPC: Book3S HV: add a VC_BASE control to the
 XIVE native device
To: Paul Mackerras <paulus@ozlabs.org>
References: <20190107184331.8429-1-clg@kaod.org>
 <20190107184331.8429-9-clg@kaod.org> <20190122051430.GE15124@blackberry>
From: =?UTF-8?Q?C=c3=a9dric_Le_Goater?= <clg@kaod.org>
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Date: Wed, 23 Jan 2019 17:56:26 +0100
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Cc: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
 David Gibson <david@gibson.dropbear.id.au>
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 <linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org>

On 1/22/19 6:14 AM, Paul Mackerras wrote:
> On Mon, Jan 07, 2019 at 07:43:20PM +0100, Cédric Le Goater wrote:
>> The ESB MMIO region controls the interrupt sources of the guest. QEMU
>> will query an fd (GET_ESB_FD ioctl) and map this region at a specific
>> address for the guest to use. The guest will obtain this information
>> using the H_INT_GET_SOURCE_INFO hcall. To inform KVM of the address
>> setting used by QEMU, add a VC_BASE control to the KVM XIVE device
> 
> This needs a little more explanation.  I *think* the only way this
> gets used is that it gets returned to the guest by the new
> hypercalls.  If that is indeed the case it would be useful to mention
> that in the patch description, because otherwise taking a value that
> userspace provides and which looks like it is an address, and not
> doing any validation on it, looks a bit scary.

I think we have solved this problem in another email thread. 

The H_INT_GET_SOURCE_INFO hcall does not need to be implemented in KVM
as all the source information should already be available in QEMU. In
that case, there is no need to inform KVM of where the ESB pages are 
mapped in the guest address space. So we don't need that extra control
on the KVM device. This is good news. 

Thanks,

C.