Re: [PATCH v10 10/13] iommu/arm-smmu-v3: Check for SVA features
From: Jean-Philippe Brucker <hidden>
Date: 2020-09-24 10:14:02
Also in:
linux-iommu, linux-mm
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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel