linux-kernel - Re: [PATCH v7 09/11] KVM: arm64: guest debug, HW assisted debug support

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Date:	Fri, 3 Jul 2015 10:23:23 +0100
From:	Will Deacon <will.deacon@....com>
To:	Alex Bennée <alex.bennee@...aro.org>
Cc:	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"kvmarm@...ts.cs.columbia.edu" <kvmarm@...ts.cs.columbia.edu>,
	"christoffer.dall@...aro.org" <christoffer.dall@...aro.org>,
	Marc Zyngier <Marc.Zyngier@....com>,
	"peter.maydell@...aro.org" <peter.maydell@...aro.org>,
	"agraf@...e.de" <agraf@...e.de>,
	"drjones@...hat.com" <drjones@...hat.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>,
	"zhichao.huang@...aro.org" <zhichao.huang@...aro.org>,
	"jan.kiszka@...mens.com" <jan.kiszka@...mens.com>,
	"dahi@...ux.vnet.ibm.com" <dahi@...ux.vnet.ibm.com>,
	"r65777@...escale.com" <r65777@...escale.com>,
	"bp@...e.de" <bp@...e.de>, Gleb Natapov <gleb@...nel.org>,
	Jonathan Corbet <corbet@....net>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	"open list:ABI/API" <linux-api@...r.kernel.org>
Subject: Re: [PATCH v7 09/11] KVM: arm64: guest debug, HW assisted debug
 support

Hi Alex,

On Thu, Jul 02, 2015 at 02:50:33PM +0100, Alex Bennée wrote:
> Are you happy with this?:

[...]

> +/**
> + * kvm_arch_dev_ioctl_check_extension
> + *
> + * We currently assume that the number of HW registers is uniform
> + * across all CPUs (see cpuinfo_sanity_check).
> + */
>  int kvm_arch_dev_ioctl_check_extension(long ext)
>  {
>         int r;
> @@ -64,6 +71,12 @@ int kvm_arch_dev_ioctl_check_extension(long ext)
>         case KVM_CAP_ARM_EL1_32BIT:
>                 r = cpu_has_32bit_el1();
>                 break;
> +       case KVM_CAP_GUEST_DEBUG_HW_BPS:
> +               r = hw_breakpoint_slots(TYPE_INST);
> +               break;
> +       case KVM_CAP_GUEST_DEBUG_HW_WPS:
> +               r  = hw_breakpoint_slots(TYPE_DATA);
> +               break;

Whilst I much prefer this code, it actually adds an unwanted dependency
on PERF_EVENTS that I didn't think about to start with. Sorry to keep
messing you about -- I guess your original patch is the best thing after
all.

Will
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