From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932556AbbFKOHn (ORCPT ); Thu, 11 Jun 2015 10:07:43 -0400 Received: from mail-wg0-f46.google.com ([74.125.82.46]:35802 "EHLO mail-wg0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753315AbbFKOHj (ORCPT ); Thu, 11 Jun 2015 10:07:39 -0400 From: Ingo Molnar To: linux-kernel@vger.kernel.org Cc: linux-mml@vger.kernel.org, Andy Lutomirski , Andrew Morton , Denys Vlasenko , Brian Gerst , Peter Zijlstra , Borislav Petkov , "H. Peter Anvin" , Linus Torvalds , Oleg Nesterov , Thomas Gleixner , Waiman Long Subject: [PATCH 03/12] x86/mm/hotplug: Don't remove PGD entries in remove_pagetable() Date: Thu, 11 Jun 2015 16:07:08 +0200 Message-Id: <1434031637-9091-4-git-send-email-mingo@kernel.org> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1434031637-9091-1-git-send-email-mingo@kernel.org> References: <1434031637-9091-1-git-send-email-mingo@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org So when memory hotplug removes a piece of physical memory from pagetable mappings, it also frees the underlying PGD entry. This complicates PGD management, so don't do this. We can keep the PGD mapped and the PUD table all clear - it's only a single 4K page per 512 GB of memory hotplugged. Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: Waiman Long Cc: linux-mm@vger.kernel.org Signed-off-by: Ingo Molnar --- arch/x86/mm/init_64.c | 27 --------------------------- 1 file changed, 27 deletions(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 1921acbd49fd..2d5931d343cd 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -770,27 +770,6 @@ static void __meminit free_pmd_table(pmd_t *pmd_start, pud_t *pud) spin_unlock(&init_mm.page_table_lock); } -/* Return true if pgd is changed, otherwise return false. */ -static bool __meminit free_pud_table(pud_t *pud_start, pgd_t *pgd) -{ - pud_t *pud; - int i; - - for (i = 0; i < PTRS_PER_PUD; i++) { - pud = pud_start + i; - if (pud_val(*pud)) - return false; - } - - /* free a pud table */ - free_pagetable(pgd_page(*pgd), 0); - spin_lock(&init_mm.page_table_lock); - pgd_clear(pgd); - spin_unlock(&init_mm.page_table_lock); - - return true; -} - static void __meminit remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end, bool direct) @@ -982,7 +961,6 @@ remove_pagetable(unsigned long start, unsigned long end, bool direct) unsigned long addr; pgd_t *pgd; pud_t *pud; - bool pgd_changed = false; for (addr = start; addr < end; addr = next) { next = pgd_addr_end(addr, end); @@ -993,13 +971,8 @@ remove_pagetable(unsigned long start, unsigned long end, bool direct) pud = (pud_t *)pgd_page_vaddr(*pgd); remove_pud_table(pud, addr, next, direct); - if (free_pud_table(pud, pgd)) - pgd_changed = true; } - if (pgd_changed) - sync_global_pgds(start, end - 1, 1); - flush_tlb_all(); } -- 2.1.4