On Mon, Sep 07, 2020 at 06:41:11PM +0200, Auger Eric wrote:

quoted

+/*
+ * Try to reserve this ASID in the SMMU. If it is in use, try to steal it from
+ * the private entry. Careful here, we may be modifying the context tables of
+ * another SMMU!

Not sure I got what you meant by this comment.

That comment does need refreshing:

/*
 * Check if the CPU ASID is available on the SMMU side. If a private context
 * descriptor is using it, try to replace it.
 */

quoted

+ */
 static struct arm_smmu_ctx_desc *
 arm_smmu_share_asid(struct mm_struct *mm, u16 asid)
 {
+	int ret;
+	u32 new_asid;
 	struct arm_smmu_ctx_desc *cd;
+	struct arm_smmu_device *smmu;
+	struct arm_smmu_domain *smmu_domain;
 
 	cd = xa_load(&arm_smmu_asid_xa, asid);
 	if (!cd)

@@ -27,8 +36,31 @@ arm_smmu_share_asid(struct mm_struct *mm, u16 asid)
 		return cd;
 	}
 
-	/* Ouch, ASID is already in use for a private cd. */
-	return ERR_PTR(-EBUSY);
+	smmu_domain = container_of(cd, struct arm_smmu_domain, s1_cfg.cd);
+	smmu = smmu_domain->smmu;
+
+	ret = xa_alloc(&arm_smmu_asid_xa, &new_asid, cd,
+		       XA_LIMIT(1, 1 << smmu->asid_bits), GFP_KERNEL);

XA_LIMIT(1, (1 << smmu->asid_bits) - 1), GFP_KERNEL)

Good catch

Thanks,
Jean


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