Re: [Xen-devel] [PATCH v4 3/3] xen/iommu: arm: Use p2m_ipa_bits as stage2 input size

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Fri, 2015-05-01 at 11:40 +1000, Edgar E. Iglesias wrote:
> From: "Edgar E. Iglesias" <edgar.iglesias@xxxxxxxxxx>
> 
> The Stage2 input-size must match what the CPU uses because
> the SMMU and the CPU share page-tables.
> 
> Test that the SMMU supports the P2M IPA bit size, use it if
> supported or bail out if not.
> 
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xxxxxxxxxx>
> ---
>  xen/drivers/passthrough/arm/smmu.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/drivers/passthrough/arm/smmu.c 
> b/xen/drivers/passthrough/arm/smmu.c
> index 8a9b58b..d9f3931 100644
> --- a/xen/drivers/passthrough/arm/smmu.c
> +++ b/xen/drivers/passthrough/arm/smmu.c
> @@ -2230,8 +2230,14 @@ static int arm_smmu_device_cfg_probe(struct 
> arm_smmu_device *smmu)
>       size = arm_smmu_id_size_to_bits((id >> ID2_IAS_SHIFT) & ID2_IAS_MASK);
>       smmu->s1_output_size = min_t(unsigned long, PHYS_MASK_SHIFT, size);
>  
> -     /* Xen: Stage-2 input size is not restricted */
> -     smmu->s2_input_size = size;
> +     /* Xen: Stage-2 input size has to match p2m_ipa_bits.  */
> +     if (size < p2m_ipa_bits) {

Referencing my question on 0/3, what if size > p2m_ipa_bits?

Do we need to also check that we are configuring the same number of
levels of PT etc, or is that already handled?

> +             dev_err(smmu->dev,
> +                     "P2M IPA size not supported (P2M=%u SMMU=%lu)!\n",
> +                     p2m_ipa_bits, size);
> +             return -ENODEV;
> +     }
> +     smmu->s2_input_size = p2m_ipa_bits;
>  #if 0
>       /* Stage-2 input size limited due to pgd allocation (PTRS_PER_PGD) */
>  #ifdef CONFIG_64BIT



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