linux-kernel - Re: [PATCH 2/7] KVM: arm: guest debug, define API headers

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Date:	Wed, 26 Nov 2014 14:14:30 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Alex Bennée <alex.bennee@...aro.org>
CC:	Peter Maydell <peter.maydell@...aro.org>,
	kvm-devel <kvm@...r.kernel.org>,
	arm-mail-list <linux-arm-kernel@...ts.infradead.org>,
	"kvmarm@...ts.cs.columbia.edu" <kvmarm@...ts.cs.columbia.edu>,
	Christoffer Dall <christoffer.dall@...aro.org>,
	Marc Zyngier <marc.zyngier@....com>,
	Alexander Graf <agraf@...e.de>,
	"J. Kiszka" <jan.kiszka@...mens.com>,
	David Hildenbrand <dahi@...ux.vnet.ibm.com>,
	Bharat Bhushan <r65777@...escale.com>, bp@...e.de,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/7] KVM: arm: guest debug, define API headers



On 26/11/2014 14:13, Alex Bennée wrote:
> 
> Paolo Bonzini <pbonzini@...hat.com> writes:
> 
>> On 25/11/2014 18:13, Peter Maydell wrote:
>>> On 25 November 2014 at 17:05, Paolo Bonzini <pbonzini@...hat.com> wrote:
>>>>> So there is no register that says "this breakpoint has triggered" or
>>>>> "this watchpoint has triggered"?
>>> Nope. You take a debug exception; the syndrome register tells
>>> you if it was a bp or a wp, and if it was a wp the fault address
>>> register tells you the address being accessed (if it was a bp
>>> you know the program counter, obviously). The debugger is expected
>>> to be able to figure it out from there, if it cares.
>>
>> That's already good enough---do the KVM_DEBUG_EXIT_* constants match the
>> syndrome register, or if not why?
> 
> No they don't. I did consider it at the time but I was wary of pulling
> too much over into the uapi headers wholesale. If your happy to do that
> I'll include the change in my next version.
> 
> I could also rationalise the exit handlers as they all pretty much do
> the same thing (save for the exit/syndrome related info). Again I was
> keeping things nicely separated in case any particular exception needed
> excessive special case handling.
> 
> Would you like those changes?

Yes, please.

Paolo
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