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From: Marc Zyngier <maz@kernel.org>
To: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2] KVM: arm64: Initialize VCPU mdcr_el2 before loading it
Date: Thu, 01 Apr 2021 16:22:40 +0100	[thread overview]
Message-ID: <87r1juowqn.wl-maz@kernel.org> (raw)
In-Reply-To: <d3f6cd69-42c8-0199-c7cd-56e1789ac141@arm.com>

On Thu, 01 Apr 2021 14:55:54 +0100,
Alexandru Elisei <alexandru.elisei@arm.com> wrote:

[...]

> Had another go at this, and as I was looking at the code, I realized that
> conceptually, trapping debug registers access (MDCR_EL2.TDA) is tied to:
> 
> - KVM_ARM64_DEBUG_DIRTY *not* being set (guest is debugging itself and KVM will
> world-switch the debug registers).
> 
> - KVM_GUESTDBG_USE_HW being set, which also *sets* KVM_ARM64_DEBUG_DIRTY (host is
> debugging the guest using hardware breakpoints).
> 
> So I cannot set the MDCR_EL2.TDA bit based on KVM_ARM64_DEBUG_DIRTY,
> because I would lose one of the two cases. It looks to me that
> keeping kvm_arm_setup_mdcr_el2() unchanged and calling it at the
> start of kvm_arm_setup_debug() is the way to go here.

Just post the revised patch, and we'll take it from there.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.

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  reply	other threads:[~2021-04-01 15:28 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-23 18:00 [PATCH v2] KVM: arm64: Initialize VCPU mdcr_el2 before loading it Alexandru Elisei
2021-03-30  9:55 ` Marc Zyngier
2021-03-30 17:13   ` Alexandru Elisei
2021-03-30 17:49     ` Alexandru Elisei
2021-03-30 19:57       ` Marc Zyngier
2021-03-31 10:48         ` Alexandru Elisei
2021-04-01 13:55         ` Alexandru Elisei
2021-04-01 15:22           ` Marc Zyngier [this message]
2021-03-30 20:07     ` Marc Zyngier
2021-03-31 15:25       ` Alexandru Elisei
2021-03-31 15:35         ` Marc Zyngier

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