Re: [Xen-devel] [PATCH v3 13/13] drivers/passthrough: arm: Add support for SMMU drivers

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-03-11 at 15:49 +0000, Julien Grall wrote:
> This patch add support for ARM architected SMMU driver. It's based on the
> linux drivers (drivers/iommu/arm-smmu) commit 89ac23cd.
> 
> The major differences with the Linux driver are:
>     - Fault by default if the SMMU is enabled to translate an
>     address (Linux is bypassing the SMMU)
>     - Using P2M page table instead of creating new one
>     - Dropped stage-1 support
>     - Dropped chained SMMUs support for now
>     - Reworking device assignment and the different structures
> 
> Xen is programming each IOMMU by:
>     - Using stage-2 mode translation
>     - Sharing the page table with the processor
>     - Injecting a fault if the device has made a wrong translation
> 
> Signed-off-by: Julien Grall<julien.grall@xxxxxxxxxx>
> Cc: Xiantao Zhang <xiantao.zhang@xxxxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>

I don't think it is sensible to try and review this code in great detail
given you no doubt did so as you imported it. I looked through the bits
which seemed like they were new Xen code rather than imported Linux
code. It mostly looks good, one question and when grammar nit.

> +static __init void arm_smmu_device_reset(struct arm_smmu_device *smmu)
> +{
> +[...]
> +    /* Don't upgrade barriers */
> +    reg &= ~(SMMU_sCR0_BSU_MASK << SMMU_sCR0_BSU_SHIFT);

No? Is that safe when a vcpu migrates around pCPUs?

> +
> +static int __init smmu_init(struct dt_device_node *dev,
> +                            const void *data)
> +{
> +    struct arm_smmu_device *smmu;
> +    int res;
> +    u64 addr, size;
> +    unsigned int num_irqs, i;
> +    struct dt_phandle_args masterspec;
> +    struct rb_node *node;
> +
> +    /* Even if the device can't be initialized, we don't want to give to
> +     * dom0 the smmu device

"we don't want to give the smmu device to dom0"

Ian.


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