linux-kernel - [PATCH] powerpc: mm: radix_tlb: rearrange the if-else block

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Message-Id: <20211125154406.470082-1-anders.roxell@linaro.org>
Date:   Thu, 25 Nov 2021 16:44:06 +0100
From:   Anders Roxell <anders.roxell@...aro.org>
To:     benh@...nel.crashing.org, paulus@...ba.org
Cc:     nathan@...nel.org, ndesaulniers@...gle.com,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Anders Roxell <anders.roxell@...aro.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: [PATCH] powerpc: mm: radix_tlb: rearrange the if-else block

Clang warns:

arch/powerpc/mm/book3s64/radix_tlb.c:1191:23: error: variable 'hstart' is uninitialized when used here [-Werror,-Wuninitialized]
                                __tlbiel_va_range(hstart, hend, pid,
                                                  ^~~~~~
arch/powerpc/mm/book3s64/radix_tlb.c:1175:23: note: initialize the variable 'hstart' to silence this warning
                unsigned long hstart, hend;
                                    ^
                                     = 0
arch/powerpc/mm/book3s64/radix_tlb.c:1191:31: error: variable 'hend' is uninitialized when used here [-Werror,-Wuninitialized]
                                __tlbiel_va_range(hstart, hend, pid,
                                                          ^~~~
arch/powerpc/mm/book3s64/radix_tlb.c:1175:29: note: initialize the variable 'hend' to silence this warning
                unsigned long hstart, hend;
                                          ^
                                           = 0
2 errors generated.

Rework the if-else to pull the 'IS_ENABLE(CONFIG_TRANSPARENT_HUGEPAGE)'
check one level up, this will silent the warnings. That will also
simplify the 'else' path. Clang is getting confused with these warnings,
but the warnings is a false-positive.

Suggested-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Anders Roxell <anders.roxell@...aro.org>
---
 arch/powerpc/mm/book3s64/radix_tlb.c | 31 +++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/mm/book3s64/radix_tlb.c b/arch/powerpc/mm/book3s64/radix_tlb.c
index 7724af19ed7e..e494a45ce1b4 100644
--- a/arch/powerpc/mm/book3s64/radix_tlb.c
+++ b/arch/powerpc/mm/book3s64/radix_tlb.c
@@ -1170,16 +1170,14 @@ static inline void __radix__flush_tlb_range(struct mm_struct *mm,
 				_tlbiel_pid_multicast(mm, pid, RIC_FLUSH_ALL);
 			}
 		}
-	} else {
+	} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
 		bool hflush = false;
 		unsigned long hstart, hend;
 
-		if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
-			hstart = (start + PMD_SIZE - 1) & PMD_MASK;
-			hend = end & PMD_MASK;
-			if (hstart < hend)
-				hflush = true;
-		}
+		hstart = (start + PMD_SIZE - 1) & PMD_MASK;
+		hend = end & PMD_MASK;
+		if (hstart < hend)
+			hflush = true;
 
 		if (type == FLUSH_TYPE_LOCAL) {
 			asm volatile("ptesync": : :"memory");
@@ -1207,6 +1205,25 @@ static inline void __radix__flush_tlb_range(struct mm_struct *mm,
 				_tlbiel_va_range_multicast(mm,
 					hstart, hend, pid, PMD_SIZE, MMU_PAGE_2M, flush_pwc);
 		}
+	} else {
+
+		if (type == FLUSH_TYPE_LOCAL) {
+			asm volatile("ptesync" : : : "memory");
+			if (flush_pwc)
+				/* For PWC, only one flush is needed */
+				__tlbiel_pid(pid, 0, RIC_FLUSH_PWC);
+			__tlbiel_va_range(start, end, pid, page_size, mmu_virtual_psize);
+			ppc_after_tlbiel_barrier();
+		} else if (cputlb_use_tlbie()) {
+			asm volatile("ptesync" : : : "memory");
+			if (flush_pwc)
+				__tlbie_pid(pid, RIC_FLUSH_PWC);
+			__tlbie_va_range(start, end, pid, page_size, mmu_virtual_psize);
+			asm volatile("eieio; tlbsync; ptesync" : : : "memory");
+		} else {
+			_tlbiel_va_range_multicast(mm,
+					start, end, pid, page_size, mmu_virtual_psize, flush_pwc);
+		}
 	}
 out:
 	preempt_enable();
-- 
2.33.0