From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AIpwx4+h/RvhJpoj3f7BhH9+BzKHC71WlvkwLud5gpy/2SEhPYYedlw47kAE4MgraKmSMT4SI1Lh ARC-Seal: i=1; a=rsa-sha256; t=1522173639; cv=none; d=google.com; s=arc-20160816; b=K47yI4MJUmw5DnXkzkS/2Xu5BbhhLm7heU6xPq1FbUxZXjv+SicFzHT6cMItl9M9ue drI1jEmiGhzeGu3gmvgCqKbHRV4LdgXvR50HjD8B2i0UDfcesdfXa5WEnC9YJxd4yvN6 YAUtXGXbHrLSy9HwhvWfgNPEtEelI7LB1nMNNxd4W8D0NCzxg2XBbklLmRIgvMy3LR7O TexRNWSoqsr/VbN08LxX46YaWtT25B9CnfZV7KbVgitddmSELvqzNFkBIYKqtxfBJWLh 5TN+d/zw9p70SNsV1sWRvJH/Y123+9frZGPyWh/U7d59o91hXb3Y8nQo+xN5bytPAOpX Xo6A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:arc-authentication-results; bh=2cQRaZj5JVDMmxUytvTdSflNCmKVcZrdwjIJmILAcdc=; b=oSxUtxC2T7ulRdrLtym3D33lCk6fX+9VyEy/w1SA5ZG+iqVpkvuDXNK+CLcCzxDGdf q81NryTWKoAVCIYrZAx5fqBQGjsy2fm4LvLIGg1WcbFeOsPlB5T4+tG0OLvPmM7v2g9O UhiWg5zU/4ZKPbyma2VEzOnlrMUCz1gbet4A/deG/lsAo4o4L6vMrnsB43hPLVPCF+oN CHk5aE7GNxsnNT9WqNnW3pOB7oZ2VEYFM5dVSJDC2F2p0o6Tl8zIaVxhWaUyN/JbM0da P+Ul2DBp0uQyWib9t2CsiBXrGebGRW0tzPYlkwbsMBzxE3z3G6J5fgJ9fswXiaDJTQbN PoHw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of will.deacon@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=will.deacon@arm.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of will.deacon@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=will.deacon@arm.com Date: Tue, 27 Mar 2018 19:00:48 +0100 From: Will Deacon To: Chintan Pandya Cc: catalin.marinas@arm.com, mark.rutland@arm.com, toshi.kani@hpe.com, arnd@arndb.de, ard.biesheuvel@linaro.org, marc.zyngier@arm.com, james.morse@arm.com, kristina.martsenko@arm.com, takahiro.akashi@linaro.org, gregkh@linuxfoundation.org, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, akpm@linux-foundation.org Subject: Re: [PATCH v5 3/4] arm64: Implement page table free interfaces Message-ID: <20180327180048.GJ18435@arm.com> References: <1522157100-16879-1-git-send-email-cpandya@codeaurora.org> <1522157100-16879-4-git-send-email-cpandya@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1522157100-16879-4-git-send-email-cpandya@codeaurora.org> User-Agent: Mutt/1.5.23 (2014-03-12) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1595007777008930452?= X-GMAIL-MSGID: =?utf-8?q?1596114745855249700?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: Hi Chintan, On Tue, Mar 27, 2018 at 06:54:59PM +0530, Chintan Pandya wrote: > Implement pud_free_pmd_page() and pmd_free_pte_page(). > > Implementation requires, > 1) Freeing of the un-used next level page tables > 2) Clearing off the current pud/pmd entry > 3) Invalidate TLB which could have previously > valid but not stale entry > > Signed-off-by: Chintan Pandya > --- > V4->V5: > - Using __flush_tlb_kernel_pgtable instead of > flush_tlb_kernel_range > > > arch/arm64/mm/mmu.c | 33 +++++++++++++++++++++++++++++++-- > 1 file changed, 31 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index da98828..3552c7a 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 +974,40 @@ int pmd_clear_huge(pmd_t *pmdp) > return 1; > } > > +static int __pmd_free_pte_page(pmd_t *pmd, unsigned long addr, bool tlb_inv) > +{ > + pmd_t *table; > + > + if (pmd_val(*pmd)) { Please can you follow what I did in 20a004e7b017 ("arm64: mm: Use READ_ONCE/WRITE_ONCE when accessing page tables") and: 1. Use consistent naming, so pmd_t * pmdp. 2. Use READ_ONCE to dereference the entry once into a local. Similarly for the pud code below. > + table = __va(pmd_val(*pmd)); > + pmd_clear(pmd); > + if (tlb_inv) > + __flush_tlb_kernel_pgtable(addr); > + > + free_page((unsigned long) table); Hmm. Surely it's only safe to call free_page if !tlb_inv in situations when the page table is already disconnected at a higher level? That doesn't appear to be the case with the function below, which still has the pud installed. What am I missing? > + } > + return 1; > +} > + > int pud_free_pmd_page(pud_t *pud, unsigned long addr) > { > - return pud_none(*pud); > + pmd_t *table; > + int i; > + > + if (pud_val(*pud)) { > + table = __va(pud_val(*pud)); > + for (i = 0; i < PTRS_PER_PMD; i++) > + __pmd_free_pte_page(&table[i], addr + (i * PMD_SIZE), > + false); > + > + pud_clear(pud); > + flush_tlb_kernel_range(addr, addr + PUD_SIZE); Why aren't you using __flush_tlb_kernel_pgtable here? Will