From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoffer Dall <christoffer.dall@linaro.org>
Subject: Re: [PATCH v2 9/9] arm64: KVM: enable trapping of all debug registers
Date: Sun, 25 May 2014 16:36:29 +0100
Message-ID: <20140525153629.GJ3866@lvm>
References: <1400604945-25247-1-git-send-email-marc.zyngier@arm.com>
 <1400604945-25247-10-git-send-email-marc.zyngier@arm.com>
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Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu,
	kvm@vger.kernel.org, Will Deacon <will.deacon@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Ian Campbell <ian.campbell@citrix.com>,
	Anup Patel <anup.patel@linaro.org>,
	Peter Maydell <peter.maydell@linaro.org>
To: Marc Zyngier <marc.zyngier@arm.com>
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On Tue, May 20, 2014 at 05:55:45PM +0100, Marc Zyngier wrote:
> Enable trapping of the debug registers, preventing the guests to
> mess with the host state (and allowing guests to use the debug
> infrastructure as well).
> 
> Reviewed-by: Anup Patel <anup.patel@linaro.org>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  arch/arm64/kvm/hyp.S | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
> index 73ec5c4..72ed0bf8 100644
> --- a/arch/arm64/kvm/hyp.S
> +++ b/arch/arm64/kvm/hyp.S
> @@ -777,6 +777,14 @@ __kvm_hyp_code_start:
>  	mrs	x2, mdcr_el2
>  	and	x2, x2, #MDCR_EL2_HPMN_MASK
>  	orr	x2, x2, #(MDCR_EL2_TPM | MDCR_EL2_TPMCR)
> +	orr	x2, x2, #(MDCR_EL2_TDRA | MDCR_EL2_TDOSA)

so we unconditionally trap on the OS register access, but we don't
properly emulate these do we?  What's the rationale?  (atmittedly,
again, I'm not 100% clear on how the OS lock thingy is supposed to
work/be used).

> +
> +	// Check for KVM_ARM64_DEBUG_DIRTY, and set to debug to trap
> +	// if not dirty.

s/set to debug to trap/set debug to trap/ ??

> +	ldr	x3, [x0, #VCPU_DEBUG_FLAGS]
> +	tbnz	x3, #KVM_ARM64_DEBUG_DIRTY_SHIFT, 1f
> +	orr	x2, x2,  #MDCR_EL2_TDA
> +1:
>  	msr	mdcr_el2, x2
>  .endm
>  
> -- 
> 1.8.3.4
> 

as per the functionality in this patch otherwise:

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>