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Date:   Wed, 17 Jun 2020 15:38:10 +0100
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Steven Price <steven.price@arm.com>
Cc:     Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>,
        James Morse <james.morse@arm.com>,
        Julien Thierry <julien.thierry.kdev@gmail.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, Dave Martin <Dave.Martin@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [RFC PATCH 2/2] arm64: kvm: Introduce MTE VCPU feature
Message-ID: <20200617143809.GF5388@gaia>
References: <20200617123844.29960-1-steven.price@arm.com>
 <20200617123844.29960-3-steven.price@arm.com>
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On Wed, Jun 17, 2020 at 01:38:44PM +0100, Steven Price wrote:
> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
> index e3b9ee268823..040a7fffaa93 100644
> --- a/virt/kvm/arm/mmu.c
> +++ b/virt/kvm/arm/mmu.c
> @@ -1783,6 +1783,17 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  			vma_pagesize = PMD_SIZE;
>  	}
>  
> +	if (system_supports_mte() && kvm->arch.vcpu_has_mte) {
> +		/*
> +		 * VM will be able to see the page's tags, so we must ensure
> +		 * they have been initialised.
> +		 */
> +		struct page *page = pfn_to_page(pfn);
> +
> +		if (!test_and_set_bit(PG_mte_tagged, &page->flags))
> +			mte_clear_page_tags(page_address(page), page_size(page));
> +	}

Are all the guest pages always mapped via a Stage 2 fault? It may be
better if we did that via kvm_set_spte_hva().

-- 
Catalin