From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933147AbeEWOBc (ORCPT ); Wed, 23 May 2018 10:01:32 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:55860 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933104AbeEWOBa (ORCPT ); Wed, 23 May 2018 10:01:30 -0400 Date: Wed, 23 May 2018 15:01:58 +0100 From: Will Deacon To: Chintan Pandya Cc: Arnd Bergmann , Mark Rutland , Ard Biesheuvel , Marc Zyngier , Andrew Morton , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Philip Elcan , James Morse , Kristina Martsenko , Toshi Kani , Dave Hansen , Vitaly Kuznetsov , Joerg Roedel , Greg Kroah-Hartman , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: [PATCH v9 3/4] arm64: Implement page table free interfaces Message-ID: <20180523140157.GG26965@arm.com> References: <1525074094-25839-1-git-send-email-cpandya@codeaurora.org> <1525074094-25839-4-git-send-email-cpandya@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1525074094-25839-4-git-send-email-cpandya@codeaurora.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Chintan, [as a side note: I'm confused on the status of this patch series, as part of it was reposted separately by Toshi. Please can you work together?] On Mon, Apr 30, 2018 at 01:11:33PM +0530, Chintan Pandya wrote: > Implement pud_free_pmd_page() and pmd_free_pte_page(). > > Implementation requires, > 1) Clearing off the current pud/pmd entry > 2) Invalidate TLB which could have previously > valid but not stale entry > 3) Freeing of the un-used next level page tables > > Signed-off-by: Chintan Pandya > --- > arch/arm64/mm/mmu.c | 29 +++++++++++++++++++++++++---- > 1 file changed, 25 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index da98828..0f651db 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -45,6 +45,7 @@ > #include > #include > #include > +#include > > #define NO_BLOCK_MAPPINGS BIT(0) > #define NO_CONT_MAPPINGS BIT(1) > @@ -973,12 +974,32 @@ int pmd_clear_huge(pmd_t *pmdp) > return 1; > } > > -int pud_free_pmd_page(pud_t *pud, unsigned long addr) > +int pmd_free_pte_page(pmd_t *pmdp, unsigned long addr) > { > - return pud_none(*pud); > + pmd_t *table; > + > + if (pmd_present(READ_ONCE(*pmdp))) { Might also be worth checking pmd_table here, just in case. (same for pud) > + table = __va(pmd_val(*pmdp)); Can you avoid dereferencing *pmdp twice, and instead READ_ONCE into a local variable, please? (same for pud) > + pmd_clear(pmdp); > + __flush_tlb_kernel_pgtable(addr); > + free_page((unsigned long) table); Shouldn't this be pte_free_kernel, to pair with pte_alloc_kernel which was used to allocate the page in the first place? (similarly for pud) > + } > + return 1; > } > > -int pmd_free_pte_page(pmd_t *pmd, unsigned long addr) > +int pud_free_pmd_page(pud_t *pudp, unsigned long addr) > { > - return pmd_none(*pmd); > + pmd_t *table; > + int i; > + > + if (pud_present(READ_ONCE(*pudp))) { > + table = __va(pud_val(*pudp)); > + for (i = 0; i < PTRS_PER_PMD; i++) > + pmd_free_pte_page(&table[i], addr + (i * PMD_SIZE)); I think it would be cleaner to write this as a do { ... } while, for consistency with the ioremap and vmalloc code. Will