[PATCH, RFC 34/62] acpi/hmat: Determine existence of an ACPI HMAT

[Kirill A. Shutemov]

From: Alison Schofield <alison.schofield@xxxxxxxxx>

Platforms that need to confirm the presence of an HMAT table
can use this function that simply reports the HMATs existence.

This is added in support of the Multi-Key Total Memory Encryption
(MKTME), a feature on future Intel platforms. These platforms will
need to confirm an HMAT is present at init time.

Signed-off-by: Alison Schofield <alison.schofield@xxxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 drivers/acpi/hmat/hmat.c | 13 +++++++++++++
 include/linux/acpi.h     |  4 ++++
 2 files changed, 17 insertions(+)

diff --git a/drivers/acpi/hmat/hmat.c b/drivers/acpi/hmat/hmat.c
index 96b7d39a97c6..38e3341f569f 100644
--- a/drivers/acpi/hmat/hmat.c
+++ b/drivers/acpi/hmat/hmat.c
@@ -664,3 +664,16 @@ static __init int hmat_init(void)
 	return 0;
 }
 subsys_initcall(hmat_init);
+
+bool acpi_hmat_present(void)
+{
+	struct acpi_table_header *tbl;
+	acpi_status status;
+
+	status = acpi_get_table(ACPI_SIG_HMAT, 0, &tbl);
+	if (ACPI_FAILURE(status))
+		return false;
+
+	acpi_put_table(tbl);
+	return true;
+}
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 75078fc9b6b3..fe3ad4ca5bb3 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1339,4 +1339,8 @@ acpi_platform_notify(struct device *dev, enum kobject_action action)
 }
 #endif
 
+#ifdef CONFIG_X86_INTEL_MKTME
+extern bool acpi_hmat_present(void);
+#endif /* CONFIG_X86_INTEL_MKTME */
+
 #endif	/*_LINUX_ACPI_H*/
-- 
2.20.1