[PATCH v2 7/7] mm: secretmem: add ability to reserve memory at boot

Mike Rapoport rppt at kernel.org
Mon Jul 27 12:29:35 EDT 2020

From: Mike Rapoport <rppt at linux.ibm.com>

Taking pages out from the direct map and bringing them back may create
undesired fragmentation and usage of the smaller pages in the direct
mapping of the physical memory.

This can be avoided if a significantly large area of the physical memory
would be reserved for secretmem purposes at boot time.

Add ability to reserve physical memory for secretmem at boot time using
"secretmem" kernel parameter and then use that reserved memory as a global
pool for secret memory needs.

Signed-off-by: Mike Rapoport <rppt at linux.ibm.com>
 Documentation/admin-guide/kernel-parameters.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index fb95fad81c79..6f3c2f28160f 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4548,6 +4548,10 @@
 			Format: integer between 0 and 10
 			Default is 0.
+	secretmem=n[KMG]
+			[KNL,BOOT] Reserve specified amount of memory to
+			back mappings of secret memory.
 	skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
 			xtime_lock contention on larger systems, and/or RCU lock
 			contention on all systems with CONFIG_MAXSMP set.

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