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Date: Tue, 18 Oct 2022 16:21:11 +0000
From: Quentin Perret <qperret@google.com>
To: Will Deacon <will@kernel.org>
Cc: kvmarm@lists.linux.dev, Sean Christopherson <seanjc@google.com>,
	Vincent Donnefort <vdonnefort@google.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	James Morse <james.morse@arm.com>,
	Chao Peng <chao.p.peng@linux.intel.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Mark Rutland <mark.rutland@arm.com>, Fuad Tabba <tabba@google.com>,
	Oliver Upton <oliver.upton@linux.dev>,
	Marc Zyngier <maz@kernel.org>, kernel-team@android.com,
	kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4 12/25] KVM: arm64: Add infrastructure to create and
 track pKVM instances at EL2
Message-ID: <Y07Sd6lVfD4IUywQ@google.com>
References: <20221017115209.2099-1-will@kernel.org>
 <20221017115209.2099-13-will@kernel.org>
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In-Reply-To: <20221017115209.2099-13-will@kernel.org>

On Monday 17 Oct 2022 at 12:51:56 (+0100), Will Deacon wrote:
> +struct pkvm_hyp_vm {
> +	struct kvm kvm;
> +
> +	/* Backpointer to the host's (untrusted) KVM instance. */
> +	struct kvm *host_kvm;
> +
> +	/*
> +	 * Total amount of memory donated by the host for maintaining
> +	 * this 'struct pkvm_hyp_vm' in the hypervisor.
> +	 */
> +	size_t donated_memory_size;

I think you could get rid of that member. IIUC, all you need to
re-compute it in the teardown path is the number of created vCPUs on
the host, which we should have safely stored in
pkvm_hyp_vm::kvm::created_vcpus.

> +	/* The guest's stage-2 page-table managed by the hypervisor. */
> +	struct kvm_pgtable pgt;
> +
> +	/*
> +	 * The number of vcpus initialized and ready to run.
> +	 * Modifying this is protected by 'vm_table_lock'.
> +	 */
> +	unsigned int nr_vcpus;
> +
> +	/* Array of the hyp vCPU structures for this VM. */
> +	struct pkvm_hyp_vcpu *vcpus[];
> +};

Cheers,
Quentin