linux-kernel - [RFC PATCH] arm64: fix the missing ktpi= cmdline check in arm64_kernel_unmapped_at

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Date:   Tue, 17 Mar 2020 19:47:08 +0800
From:   Hongbo Yao <yaohongbo@...wei.com>
To:     <will@...nel.org>, <broonie@...nel.org>
CC:     <yaohongbo@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH] arm64: fix the missing ktpi= cmdline check in arm64_kernel_unmapped_at_el0()

Kpti cannot be disabled from the kernel cmdline after the commit
09e3c22a("arm64: Use a variable to store non-global mappings decision").

Bring back the missing check of kpti= command-line option to fix the
case where the SPE driver complains the missing "kpti-off" even it has
already been set.

Signed-off-by: Hongbo Yao <yaohongbo@...wei.com>
---
 arch/arm64/include/asm/mmu.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 3c9533322558..ebbc0d3ac2f7 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -34,7 +34,8 @@ extern bool arm64_use_ng_mappings;
 
 static inline bool arm64_kernel_unmapped_at_el0(void)
 {
-	return arm64_use_ng_mappings;
+	return arm64_use_ng_mappings &&
+		cpus_have_const_cap(ARM64_UNMAP_KERNEL_AT_EL0);
 }
 
 typedef void (*bp_hardening_cb_t)(void);
-- 
2.20.1