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[23.128.96.18]) by mx.google.com with ESMTP id x22si7784607ejv.520.2020.07.03.06.40.06; Fri, 03 Jul 2020 06:40:28 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=A2YWVWIR; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726682AbgGCNjn (ORCPT + 99 others); Fri, 3 Jul 2020 09:39:43 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:35416 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726048AbgGCNjl (ORCPT ); Fri, 3 Jul 2020 09:39:41 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1593783579; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=aFIJGKtM6VwVokH8Ga5bRfXr8MdIFlAYKMZ3yizveMM=; b=A2YWVWIR6mqhBBTmBggn1T165/WXjBpoXh/juY0WB3RjGSVKwA3Y/Y5f2bY2LvF5rFCEgI DjKtRA7vd04ebteWbJ4/SqBDbFkGkgfBsE/k/136223vJ9TtfagwPGlwRTgSg7M6yEfeAr yUD1TfXdUuuk687OU8jv6rA+5mbGJB4= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-403-dtpxDSbmOoW9xbObZr_6Xw-1; Fri, 03 Jul 2020 09:39:35 -0400 X-MC-Unique: dtpxDSbmOoW9xbObZr_6Xw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1B609107ACCA; Fri, 3 Jul 2020 13:39:34 +0000 (UTC) Received: from t480s.redhat.com (ovpn-114-0.ams2.redhat.com [10.36.114.0]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7943271690; Fri, 3 Jul 2020 13:39:32 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-s390@vger.kernel.org, linux-mm@kvack.org, David Hildenbrand , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Gerald Schaefer Subject: [PATCH v1 6/9] s390/vmem: cleanup empty page tables Date: Fri, 3 Jul 2020 15:39:14 +0200 Message-Id: <20200703133917.39045-7-david@redhat.com> In-Reply-To: <20200703133917.39045-1-david@redhat.com> References: <20200703133917.39045-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Let's cleanup empty page tables. Consider only page tables that fully fall into the idendity mapping and the vmemmap range. As there are no valid accesses to vmem/vmemmap within non-populated ranges, the single tlb flush at the end should be sufficient. Cc: Heiko Carstens Cc: Vasily Gorbik Cc: Christian Borntraeger Cc: Gerald Schaefer Signed-off-by: David Hildenbrand --- arch/s390/mm/vmem.c | 98 ++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 97 insertions(+), 1 deletion(-) diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c index aa968f67d7f9f..5239130770b7b 100644 --- a/arch/s390/mm/vmem.c +++ b/arch/s390/mm/vmem.c @@ -63,6 +63,15 @@ pte_t __ref *vmem_pte_alloc(void) return pte; } +static void vmem_pte_free(unsigned long *table) +{ + /* We don't expect boot memory to be removed ever. */ + if (!slab_is_available() || + WARN_ON_ONCE(PageReserved(virt_to_page(table)))) + return; + page_table_free(&init_mm, table); +} + /* * Add a physical memory range to the 1:1 mapping. */ @@ -168,6 +177,21 @@ static void remove_pte_table(pmd_t *pmd, unsigned long addr, update_page_count(PG_DIRECT_MAP_4K, -pages); } +static void try_free_pte_table(pmd_t *pmd, unsigned long start) +{ + pte_t *pte; + int i; + + /* We can safely assume this is fully in 1:1 mapping & vmemmap area */ + pte = pte_offset_kernel(pmd, start); + for (i = 0; i < PTRS_PER_PTE; i++, pte++) + if (!pte_none(*pte)) + return; + + vmem_pte_free(__va(pmd_deref(*pmd))); + pmd_clear(pmd); +} + static void remove_pmd_table(pud_t *pud, unsigned long addr, unsigned long end, bool direct) { @@ -194,12 +218,36 @@ static void remove_pmd_table(pud_t *pud, unsigned long addr, } remove_pte_table(pmd, addr, next, direct); + try_free_pte_table(pmd, addr & PMD_MASK); } if (direct) update_page_count(PG_DIRECT_MAP_1M, -pages); } +static void try_free_pmd_table(pud_t *pud, unsigned long start) +{ + const unsigned long end = start + PUD_SIZE; + pmd_t *pmd; + int i; + + /* Don't mess with any tables not fully in 1:1 mapping & vmemmap area */ + if (end > VMALLOC_START) + return; +#ifdef CONFIG_KASAN + if (start < KASAN_SHADOW_END && KASAN_SHADOW_START > end) + return; +#endif + + pmd = pmd_offset(pud, start); + for (i = 0; i < PTRS_PER_PMD; i++, pmd++) + if (!pmd_none(*pmd)) + return; + + vmem_free_pages(pud_deref(*pud), CRST_ALLOC_ORDER); + pud_clear(pud); +} + static void remove_pud_table(p4d_t *p4d, unsigned long addr, unsigned long end, bool direct) { @@ -224,12 +272,36 @@ static void remove_pud_table(p4d_t *p4d, unsigned long addr, } remove_pmd_table(pud, addr, next, direct); + try_free_pmd_table(pud, addr & PUD_MASK); } if (direct) update_page_count(PG_DIRECT_MAP_2G, -pages); } +static void try_free_pud_table(p4d_t *p4d, unsigned long start) +{ + const unsigned long end = start + P4D_SIZE; + pud_t *pud; + int i; + + /* Don't mess with any tables not fully in 1:1 mapping & vmemmap area */ + if (end > VMALLOC_START) + return; +#ifdef CONFIG_KASAN + if (start < KASAN_SHADOW_END && KASAN_SHADOW_START > end) + return; +#endif + + pud = pud_offset(p4d, start); + for (i = 0; i < PTRS_PER_PUD; i++, pud++) + if (!pud_none(*pud)) + return; + + vmem_free_pages(p4d_deref(*p4d), CRST_ALLOC_ORDER); + p4d_clear(p4d); +} + static void remove_p4d_table(pgd_t *pgd, unsigned long addr, unsigned long end, bool direct) { @@ -244,9 +316,33 @@ static void remove_p4d_table(pgd_t *pgd, unsigned long addr, continue; remove_pud_table(p4d, addr, next, direct); + try_free_pud_table(p4d, addr & P4D_MASK); } } +static void try_free_p4d_table(pgd_t *pgd, unsigned long start) +{ + const unsigned long end = start + PGDIR_SIZE; + p4d_t *p4d; + int i; + + /* Don't mess with any tables not fully in 1:1 mapping & vmemmap area */ + if (end > VMALLOC_START) + return; +#ifdef CONFIG_KASAN + if (start < KASAN_SHADOW_END && KASAN_SHADOW_START > end) + return; +#endif + + p4d = p4d_offset(pgd, start); + for (i = 0; i < PTRS_PER_P4D; i++, p4d++) + if (!p4d_none(*p4d)) + return; + + vmem_free_pages(pgd_deref(*pgd), CRST_ALLOC_ORDER); + pgd_clear(pgd); +} + static void remove_pagetable(unsigned long start, unsigned long end, bool direct) { @@ -264,6 +360,7 @@ static void remove_pagetable(unsigned long start, unsigned long end, continue; remove_p4d_table(pgd, addr, next, direct); + try_free_p4d_table(pgd, addr & PGDIR_MASK); } flush_tlb_kernel_range(start, end); @@ -271,7 +368,6 @@ static void remove_pagetable(unsigned long start, unsigned long end, /* * Remove a physical memory range from the 1:1 mapping. - * Currently only invalidates page table entries. */ static void vmem_remove_range(unsigned long start, unsigned long size) { -- 2.26.2