linux-kernel - [PATCH V8 06/44] mm/pkeys: Add Kconfig options for PKS

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Message-Id: <20220127175505.851391-7-ira.weiny@intel.com>
Date:   Thu, 27 Jan 2022 09:54:27 -0800
From:   ira.weiny@...el.com
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     Ira Weiny <ira.weiny@...el.com>, Fenghua Yu <fenghua.yu@...el.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH V8 06/44] mm/pkeys: Add Kconfig options for PKS

From: Ira Weiny <ira.weiny@...el.com>

Protection Key Supervisor, PKS, is a feature used by kernel code only.
As such if no kernel users are configured the PKS code is unnecessary
overhead.

Define a Kconfig structure which allows kernel code to detect PKS
support by an architecture and then subsequently enable that support
within the architecture.

ARCH_HAS_SUPERVISOR_PKEYS indicates to kernel consumers that an
architecture supports pkeys.  PKS users can then select
ARCH_ENABLE_SUPERVISOR_PKEYS to turn on the support within the
architecture.

If ARCH_ENABLE_SUPERVISOR_PKEYS is not selected architectures avoid the
PKS overhead.

ARCH_ENABLE_SUPERVISOR_PKEYS remains off until the first kernel use case
sets it.

Signed-off-by: Ira Weiny <ira.weiny@...el.com>

---
Changes for V8
	Split this out to a single change patch
---
 arch/x86/Kconfig | 1 +
 mm/Kconfig       | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ebe8fc76949a..a30fe85e27ac 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1867,6 +1867,7 @@ config X86_INTEL_MEMORY_PROTECTION_KEYS
 	depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
 	select ARCH_USES_HIGH_VMA_FLAGS
 	select ARCH_HAS_PKEYS
+	select ARCH_HAS_SUPERVISOR_PKEYS
 	help
 	  Memory Protection Keys provides a mechanism for enforcing
 	  page-based protections, but without requiring modification of the
diff --git a/mm/Kconfig b/mm/Kconfig
index 3326ee3903f3..46f2bb15aa4e 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -804,6 +804,10 @@ config ARCH_USES_HIGH_VMA_FLAGS
 	bool
 config ARCH_HAS_PKEYS
 	bool
+config ARCH_HAS_SUPERVISOR_PKEYS
+	bool
+config ARCH_ENABLE_SUPERVISOR_PKEYS
+	bool
 
 config PERCPU_STATS
 	bool "Collect percpu memory statistics"
-- 
2.31.1