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

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Date:	Wed, 26 Nov 2014 13:13:25 +0000
From:	Alex Bennée <alex.bennee@...aro.org>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	Peter Maydell <peter.maydell@...aro.org>,
	kvm-devel <kvm@...r.kernel.org>,
	arm-mail-list <linux-arm-kernel@...ts.infradead.org>,
	"kvmarm\@lists.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


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?

>
> Paolo

-- 
Alex Bennée
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