linux-kernel - [PATCH] arm64: Cleanup __cpu_set_tcr

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Date: Thu, 23 May 2024 21:21:46 +0900
From: Seongsu Park <sgsu.park@...sung.com>
To: catalin.marinas@....com, will@...nel.org, ardb@...nel.org,
	mark.rutland@....com
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	infinite.run@...il.com, sgsu.park@...sung.com
Subject: [PATCH] arm64: Cleanup __cpu_set_tcr_t0sz()

The T0SZ field of TCR_EL1 occupies bits 0-5 of the register and encode
the virtual address space translated by TTBR0_EL1. When updating the
field, for example because we are switching to/from the idmap page-table,
__cpu_set_tcr_t0sz() erroneously treats its 't0sz' argument as unshifted,
resulting in harmless but confusing double shifts by 0 in the code.

Co-developed-by: Leem ChaeHoon <infinite.run@...il.com>
Signed-off-by: Leem ChaeHoon <infinite.run@...il.com>
Signed-off-by: Seongsu Park <sgsu.park@...sung.com>
---
 arch/arm64/include/asm/mmu_context.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
index c768d16b81a4..bd19f4c758b7 100644
--- a/arch/arm64/include/asm/mmu_context.h
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -72,11 +72,11 @@ static inline void __cpu_set_tcr_t0sz(unsigned long t0sz)
 {
 	unsigned long tcr = read_sysreg(tcr_el1);
 
-	if ((tcr & TCR_T0SZ_MASK) >> TCR_T0SZ_OFFSET == t0sz)
+	if ((tcr & TCR_T0SZ_MASK) == t0sz)
 		return;
 
 	tcr &= ~TCR_T0SZ_MASK;
-	tcr |= t0sz << TCR_T0SZ_OFFSET;
+	tcr |= t0sz;
 	write_sysreg(tcr, tcr_el1);
 	isb();
 }
-- 
2.34.1