From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752673AbeFDMM7 (ORCPT ); Mon, 4 Jun 2018 08:12:59 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:42354 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751769AbeFDMM6 (ORCPT ); Mon, 4 Jun 2018 08:12:58 -0400 Date: Mon, 4 Jun 2018 13:13:28 +0100 From: Will Deacon To: Chintan Pandya Cc: catalin.marinas@arm.com, mark.rutland@arm.com, akpm@linux-foundation.org, toshi.kani@hpe.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v12 4/5] arm64: Implement page table free interfaces Message-ID: <20180604121328.GG9482@arm.com> References: <1527856758-27169-1-git-send-email-cpandya@codeaurora.org> <1527856758-27169-5-git-send-email-cpandya@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1527856758-27169-5-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 On Fri, Jun 01, 2018 at 06:09:17PM +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 Please can you rewrite this describing the problem that you're solving, rather than a brief summary of some requirements? > Signed-off-by: Chintan Pandya > --- > arch/arm64/mm/mmu.c | 38 ++++++++++++++++++++++++++++++++++---- > 1 file changed, 34 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 8ae5d7a..6e7e16c 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) > @@ -977,12 +978,41 @@ 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); > + pte_t *table; > + pmd_t pmd; > + > + pmd = READ_ONCE(*pmdp); > + if (pmd_present(pmd)) { > + table = pmd_page_vaddr(pmd); > + pmd_clear(pmdp); > + __flush_tlb_kernel_pgtable(addr); > + pte_free_kernel(NULL, table); > + } > + 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; > + pmd_t *entry; > + pud_t pud; > + unsigned long next, end; > + > + pud = READ_ONCE(*pudp); > + if (pud_present(pud)) { Just some stylistic stuff, but please can you rewrite this as: if (!pud_present(pud) || VM_WARN_ON(!pud_table(pud))) return 1; similarly for the pmd/pte code above. > + table = pud_page_vaddr(pud); > + entry = table; Could you rename entry -> pmdp, please? > + next = addr; > + end = addr + PUD_SIZE; > + do { > + pmd_free_pte_page(entry, next); > + } while (entry++, next += PMD_SIZE, next != end); > + > + pud_clear(pudp); > + __flush_tlb_kernel_pgtable(addr); > + pmd_free(NULL, table); > + } > + return 1; So with these patches, we only ever return 1 from these helpers. It looks like the same is true for x86, so how about we make them void and move the calls inside the conditionals in lib/ioremap.c? Obviously, this would be a separate patch on the end. Will