linux-kernel - Re: [PATCH v3 24/32] KVM: arm64: Reserve memory for host stage 2

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Date:   Thu, 4 Mar 2021 19:49:53 +0000
From:   Will Deacon <will@...nel.org>
To:     Quentin Perret <qperret@...gle.com>
Cc:     catalin.marinas@....com, maz@...nel.org, james.morse@....com,
        julien.thierry.kdev@...il.com, suzuki.poulose@....com,
        android-kvm@...gle.com, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, kvmarm@...ts.cs.columbia.edu,
        linux-arm-kernel@...ts.infradead.org, tabba@...gle.com,
        mark.rutland@....com, dbrazdil@...gle.com, mate.toth-pal@....com,
        seanjc@...gle.com, robh+dt@...nel.org
Subject: Re: [PATCH v3 24/32] KVM: arm64: Reserve memory for host stage 2

On Tue, Mar 02, 2021 at 02:59:54PM +0000, Quentin Perret wrote:
> Extend the memory pool allocated for the hypervisor to include enough
> pages to map all of memory at page granularity for the host stage 2.
> While at it, also reserve some memory for device mappings.
> 
> Signed-off-by: Quentin Perret <qperret@...gle.com>
> ---
>  arch/arm64/kvm/hyp/include/nvhe/mm.h | 23 ++++++++++++++++++++++-
>  arch/arm64/kvm/hyp/nvhe/setup.c      | 12 ++++++++++++
>  arch/arm64/kvm/hyp/reserved_mem.c    |  2 ++
>  3 files changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/mm.h b/arch/arm64/kvm/hyp/include/nvhe/mm.h
> index ac0f7fcffd08..411a35db949c 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/mm.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/mm.h
> @@ -53,7 +53,7 @@ static inline unsigned long __hyp_pgtable_max_pages(unsigned long nr_pages)
>  	return total;
>  }
>  
> -static inline unsigned long hyp_s1_pgtable_pages(void)
> +static inline unsigned long __hyp_pgtable_total_pages(void)
>  {
>  	unsigned long res = 0, i;
>  
> @@ -63,9 +63,30 @@ static inline unsigned long hyp_s1_pgtable_pages(void)
>  		res += __hyp_pgtable_max_pages(reg->size >> PAGE_SHIFT);
>  	}
>  
> +	return res;
> +}
> +
> +static inline unsigned long hyp_s1_pgtable_pages(void)
> +{
> +	unsigned long res;
> +
> +	res = __hyp_pgtable_total_pages();
> +
>  	/* Allow 1 GiB for private mappings */
>  	res += __hyp_pgtable_max_pages(SZ_1G >> PAGE_SHIFT);
>  
>  	return res;
>  }
> +
> +static inline unsigned long host_s2_mem_pgtable_pages(void)
> +{
> +	return __hyp_pgtable_total_pages() + 16;

Is this 16 due to the possibility of a concatenated pgd? If so, please add
a comment to that effect.

With that:

Acked-by: Will Deacon <will@...nel.org>

Will