Recap discussion on the other thread.
https://lore.kernel.org/linux-mm/camkat6qorwbaxapacasm0sc9o2uq9zqzb6s1kbkvav2d4tk...@mail.gmail.com/#t
On 6/16/2022 8:55 AM, Suravee Suthikulpanit wrote:
+int amd_iommu_snp_enable(void)
+{
+ /*
+ * The SNP support requires that IOMMU must be enabled, and is
+ * not configured in the passthrough mode.
+ */
+ if (no_iommu || iommu_default_passthrough()) {
+ pr_err("SNP: IOMMU is either disabled or configured in passthrough
mode.\n");
+ return -EINVAL;
+ }
Peter has suggested rewording to something more descriptive such as:
"SNP: IOMMU is either disabled or configured in passthrough mode, SNP cannot be
supported".
Thank you,
Suravee
+ /*
+ * Prevent enabling SNP after IOMMU_ENABLED state because this process
+ * affect how IOMMU driver sets up data structures and configures
+ * IOMMU hardware.
+ */
+ if (init_state > IOMMU_ENABLED) {
+ pr_err("SNP: Too late to enable SNP for IOMMU.\n");
+ return -EINVAL;
+ }
+
+ amd_iommu_snp_en = amd_iommu_snp_sup;
+ if (!amd_iommu_snp_en)
+ return -EINVAL;
+
+ pr_info("SNP enabled\n");
+
+ /* Enforce IOMMU v1 pagetable when SNP is enabled. */
+ if (amd_iommu_pgtable != AMD_IOMMU_V1) {
+ pr_warn("Force to using AMD IOMMU v1 page table due to SNP\n");
+ amd_iommu_pgtable = AMD_IOMMU_V1;
+ amd_iommu_ops.pgsize_bitmap = AMD_IOMMU_PGSIZES;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(amd_iommu_snp_enable);
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