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Shutemov" , Ingo Molnar , Steve Wahl Subject: Re: [Patch v3] x86/head/64: remove redundant check on level2_kernel_pgt's _PAGE_PRESENT bit Message-ID: <20240705071246.wzl224vveysrunzc@master> Reply-To: Wei Yang References: <20240523123539.14260-1-richard.weiyang@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240523123539.14260-1-richard.weiyang@gmail.com> User-Agent: NeoMutt/20170113 (1.7.2) May I ask what else I should do? On Thu, May 23, 2024 at 12:35:39PM +0000, Wei Yang wrote: >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 > >level2_kernel_pgt compiled with _PAGE_PRESENT set. The check is >redundant > >Signed-off-by: Wei Yang >CC: Thomas Gleixner >CC: Kirill A. Shutemov >CC: Ingo Molnar >CC: Steve Wahl > >--- >v3: refine the change log per kirill's comment >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 -- Wei Yang Help you, Help me