linux-kernel - Re: [PATCH v5 04/13] KVM: Introduce a new guest mapping API

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Message-ID: <20190123175014.GK19289@Konrads-MacBook-Pro.local>
Date:   Wed, 23 Jan 2019 12:50:18 -0500
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     KarimAllah Ahmed <karahmed@...zon.de>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        pbonzini@...hat.com, rkrcmar@...hat.com
Subject: Re: [PATCH v5 04/13] KVM: Introduce a new guest mapping API

> +	if (dirty)
> +		kvm_release_pfn_dirty(map->pfn);
> +	else
> +		kvm_release_pfn_clean(map->pfn);
> +	map->hva = NULL;

I keep on having this gnawing feeling that we MUST set map->page to
NULL.

That is I can see how it is not needed if you are using 'map' and
'unmap' together - for that we are good. But what I am worried is that
some one unmaps it .. and instead of checking map->hva they end up
checking map->page and think the page is mapped.

Would you be OK adding that extra statement just as a fail-safe
mechanism in case someones misues the APIs?