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Shutemov" , Ingo Molnar , Steve Wahl Subject: [Patch v2] x86/head/64: remove redundant check on level2_kernel_pgt's _PAGE_PRESENT bit Date: Thu, 23 May 2024 08:37:52 +0000 Message-Id: <20240523083752.11426-1-richard.weiyang@gmail.com> X-Mailer: git-send-email 2.11.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: This patch tries to remove a redundant check on kernel code's PMD _PAGE_PRESENT attribute before fix up. Current process looks like this: pmd in [0, _text) unset _PAGE_PRESENT pmd in [_text, _end] if (_PAGE_PRESENT) fix up delta pmd in (_end, 512) unset _PAGE_PRESENT Since we have compiled in _PAGE_PRESENT in this page table, it is not necessary to check _PAGE_PRESENT again before fixing up delta Signed-off-by: Wei Yang CC: Thomas Gleixner CC: Kirill A. Shutemov CC: Ingo Molnar CC: Steve Wahl --- v2: adjust the change log to emphasize the redundant check --- arch/x86/kernel/head64.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index a817ed0724d1..bac33ec19aa2 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -260,8 +260,7 @@ unsigned long __head __startup_64(unsigned long physaddr, /* fixup pages that are part of the kernel image */ for (; i <= pmd_index((unsigned long)_end); i++) - if (pmd[i] & _PAGE_PRESENT) - pmd[i] += load_delta; + pmd[i] += load_delta; /* invalidate pages after the kernel image */ for (; i < PTRS_PER_PMD; i++) -- 2.34.1