linux-kernel - [PATCH 2/3] ARC: build: disallow invalid PAE40 + 4K page config

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Message-ID: <20241016052749.1640081-3-vgupta@kernel.org>
Date: Tue, 15 Oct 2024 22:27:48 -0700
From: Vineet Gupta <vgupta@...nel.org>
To: linux-snps-arc@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org,
	Vineet Gupta <vgupta@...nel.org>,
	kernel test robot <lkp@...el.com>
Subject: [PATCH 2/3] ARC: build: disallow invalid PAE40 + 4K page config

The config option being built was
| CONFIG_ARC_MMU_V4=y
| CONFIG_ARC_PAGE_SIZE_4K=y
| CONFIG_HIGHMEM=y
| CONFIG_ARC_HAS_PAE40=y

This was hitting a BUILD_BUG_ON() since a 4K page can't hoist 1k, 8-byte
PTE entries (8 byte due to PAE40). BUILD_BUG_ON() is a good last ditch
resort, but such a config needs to be disallowed explicitly in Kconfig.

Side-note: the actual fix is single liner dependency, but while at it
cleaned out a few things:
 - 4K dependency on MMU v3 or v4 is always true, since 288ff7de62af09
   ("ARC: retire MMUv1 and MMUv2 support")
 - PAE40 dependency in on MMU ver not really ISA, although that follows
   eventually.

Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202409160223.xydgucbY-lkp@intel.com/
Signed-off-by: Vineet Gupta <vgupta@...nel.org>
---
 arch/arc/Kconfig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 5b2488142041..69c6e71fa1e6 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -297,7 +297,6 @@ config ARC_PAGE_SIZE_16K
 config ARC_PAGE_SIZE_4K
 	bool "4KB"
 	select HAVE_PAGE_SIZE_4KB
-	depends on ARC_MMU_V3 || ARC_MMU_V4
 
 endchoice
 
@@ -474,7 +473,8 @@ config HIGHMEM
 
 config ARC_HAS_PAE40
 	bool "Support for the 40-bit Physical Address Extension"
-	depends on ISA_ARCV2
+	depends on MMU_V4
+	depends on !ARC_PAGE_SIZE_4K
 	select HIGHMEM
 	select PHYS_ADDR_T_64BIT
 	help
-- 
2.43.0