Re: [PATCH] powerpc: mm: radix_tlb: rearrange the if-else block
flat view
From: Christophe Leroy <hidden>
Date: 2021-11-26 13:45:30
Also in:
lkml, llvm
Le 25/11/2021 à 16:44, Anders Roxell a écrit :
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.But you are duplicating a significant part of the code by doing that, and duplicated code generaly leads to bugs. And we already have redundant stuff between FLUSH_TYPE_LOCAL leg and cputlb_use_tlbie() leg. Can't you fix CLANG instead :) ? Or just add an else to the IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) that sets hstart and hend to 0 ? Or just put hstart and hend calculation outside the IS_ENABLED() ? After all GCC should drop the calculation when not used.
quoted hunk ↗ jump to hunk
Suggested-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Anders Roxell <redacted> --- 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();