[PATCH, RFC 36/62] acpi/hmat: Evaluate topology presented in ACPI HMAT for MKTME

[Kirill A. Shutemov]

From: Alison Schofield <alison.schofield@xxxxxxxxx>

MKTME, Multi-Key Total Memory Encryption, is a feature on Intel
platforms. The ACPI HMAT table can be used to verify that the
platform topology is safe for the usage of MKTME.

The kernel must be capable of programming every memory controller
on the platform. This means that there must be a CPU online, in
the same proximity domain of each memory controller.

Signed-off-by: Alison Schofield <alison.schofield@xxxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 drivers/acpi/hmat/hmat.c | 54 ++++++++++++++++++++++++++++++++++++++++
 include/linux/acpi.h     |  1 +
 2 files changed, 55 insertions(+)

diff --git a/drivers/acpi/hmat/hmat.c b/drivers/acpi/hmat/hmat.c
index 38e3341f569f..936a403c0694 100644
--- a/drivers/acpi/hmat/hmat.c
+++ b/drivers/acpi/hmat/hmat.c
@@ -677,3 +677,57 @@ bool acpi_hmat_present(void)
 	acpi_put_table(tbl);
 	return true;
 }
+
+static int mktme_parse_proximity_domains(union acpi_subtable_headers *header,
+					 const unsigned long end)
+{
+	struct acpi_hmat_proximity_domain *mar = (void *)header;
+	struct acpi_hmat_structure *hdr = (void *)header;
+
+	const struct cpumask *tmp_mask;
+
+	if (!hdr || hdr->type != ACPI_HMAT_TYPE_PROXIMITY)
+		return -EINVAL;
+
+	if (mar->header.length != sizeof(*mar)) {
+		pr_warn("MKTME: invalid header length in HMAT\n");
+		return -1;
+	}
+	/*
+	 * Require a valid processor proximity domain.
+	 * This will catch memory only physical packages with
+	 * no processor capable of programming the key table.
+	 */
+	if (!(mar->flags & ACPI_HMAT_PROCESSOR_PD_VALID)) {
+		pr_warn("MKTME: no valid processor proximity domain\n");
+		return -1;
+	}
+	/* Require an online CPU in the processor proximity domain. */
+	tmp_mask = cpumask_of_node(pxm_to_node(mar->processor_PD));
+	if (!cpumask_intersects(tmp_mask, cpu_online_mask)) {
+		pr_warn("MKTME: no online CPU in proximity domain\n");
+		return -1;
+	}
+	return 0;
+}
+
+/* Returns true if topology is safe for MKTME key creation */
+bool mktme_hmat_evaluate(void)
+{
+	struct acpi_table_header *tbl;
+	bool ret = true;
+	acpi_status status;
+
+	status = acpi_get_table(ACPI_SIG_HMAT, 0, &tbl);
+	if (ACPI_FAILURE(status))
+		return -EINVAL;
+
+	if (acpi_table_parse_entries(ACPI_SIG_HMAT,
+				     sizeof(struct acpi_table_hmat),
+				     ACPI_HMAT_TYPE_PROXIMITY,
+				     mktme_parse_proximity_domains, 0) < 0) {
+		ret = false;
+	}
+	acpi_put_table(tbl);
+	return ret;
+}
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index fe3ad4ca5bb3..82b270dfb785 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1341,6 +1341,7 @@ acpi_platform_notify(struct device *dev, enum kobject_action action)
 
 #ifdef CONFIG_X86_INTEL_MKTME
 extern bool acpi_hmat_present(void);
+extern bool mktme_hmat_evaluate(void);
 #endif /* CONFIG_X86_INTEL_MKTME */
 
 #endif	/*_LINUX_ACPI_H*/
-- 
2.20.1