Hi Shameer,

On Mon, Sep 21, 2020 at 08:59:39AM +0000, Shameerali Kolothum Thodi wrote:

quoted

+bool arm_smmu_sva_supported(struct arm_smmu_device *smmu)
+{
+	unsigned long reg, fld;
+	unsigned long oas;
+	unsigned long asid_bits;
+	u32 feat_mask = ARM_SMMU_FEAT_BTM |
ARM_SMMU_FEAT_COHERENCY;

Why is BTM mandated for SVA? I couldn't find this requirement in SMMU spec
(Sorry if I missed it or this got discussed earlier). But if performance is the only concern here,
is it better just to allow it with a warning rather than limiting SMMUs without BTM?

It's a performance concern and requires to support multiple
configurations, but the spec allows it. Are there SMMUs without BTM that
need it?

Thanks,
Jean

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