From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alex =?utf-8?Q?Benn=C3=A9e?= <alex.bennee@linaro.org>
Subject: Re: Exposing host debug capabilities to userspace
Date: Mon, 24 Nov 2014 12:53:00 +0000
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Cc: Peter Maydell <peter.maydell@linaro.org>,
	Will Deacon <will.deacon@arm.com>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Christoffer Dall <christoffer.dall@linaro.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	"kvmarm\@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
	KVM devel mailing list <kvm@vger.kernel.org>
To: Alexander Graf <agraf@suse.de>
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Alexander Graf <agraf@suse.de> writes:

>> Am 24.11.2014 um 13:32 schrieb Peter Maydell <peter.maydell@linaro.o=
rg>:
>>=20
>>> On 24 November 2014 at 12:26, Alexander Graf <agraf@suse.de> wrote:
>>> On 24.11.14 12:35, Alex Benn=C3=A9e wrote:
>>>>> * KVM ioctl GET_ONE_REG(ID_AA64DFR0_EL1)
>>>> Nope, guest state API
>>>=20
>>> What's the problem with using ONE_REG for this? After all, the tota=
l
>>> number of available guest debug register is a guest vcpu property o=
f
>>> some sort.
>>=20
>> Yes, but we don't want to know about properties of the guest
>> vCPU. In an ideal world QEMU could reserve say half the debug
>> registers for debugging the VM on startup and have KVM expose
>> ID registers indicating to the guest that it only had the
>> other half...
>
> Yup, so create another (read-only) ONE_REG that exposes the number of
> actual guest debug registers.

Does the GET/SET_ONE_REG have the concept of a read-only register? I'd
be worried by code just blindly iterating over the lists getting thrown
when one doesn't work.

>
> Alex
>
>>=20
>> -- PMM

--=20
Alex Benn=C3=A9e