Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934760AbaFJAX1 (ORCPT ); Mon, 9 Jun 2014 20:23:27 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:58627 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934679AbaFJAWw (ORCPT ); Mon, 9 Jun 2014 20:22:52 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Kiper , Konrad Rzeszutek Wilk Subject: [PATCH 3.4 88/88] xen/p2m: Reuse existing P2M leafs if they are filled with 1:1 PFNs or INVALID. Date: Mon, 9 Jun 2014 17:25:38 -0700 Message-Id: <20140610002427.393098381@linuxfoundation.org> X-Mailer: git-send-email 1.9.0 In-Reply-To: <20140610002424.500996570@linuxfoundation.org> References: <20140610002424.500996570@linuxfoundation.org> User-Agent: quilt/0.63-1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Konrad Rzeszutek Wilk commit 250a41e0ecc433cdd553a364d0fc74c766425209 upstream. If P2M leaf is completly packed with INVALID_P2M_ENTRY or with 1:1 PFNs (so IDENTITY_FRAME type PFNs), we can swap the P2M leaf with either a p2m_missing or p2m_identity respectively. The old page (which was created via extend_brk or was grafted on from the mfn_list) can be re-used for setting new PFNs. This also means we can remove git commit: 5bc6f9888db5739abfa0cae279b4b442e4db8049 xen/p2m: Reserve 8MB of _brk space for P2M leafs when populating back which tried to fix this. and make the amount that is required to be reserved much smaller. Signed-off-by: Daniel Kiper Signed-off-by: Konrad Rzeszutek Wilk Signed-off-by: Greg Kroah-Hartman --- arch/x86/xen/p2m.c | 95 +++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 92 insertions(+), 3 deletions(-) --- a/arch/x86/xen/p2m.c +++ b/arch/x86/xen/p2m.c @@ -196,9 +196,11 @@ RESERVE_BRK(p2m_mid_identity, PAGE_SIZE /* When we populate back during bootup, the amount of pages can vary. The * max we have is seen is 395979, but that does not mean it can't be more. - * But some machines can have 3GB I/O holes even. So lets reserve enough - * for 4GB of I/O and E820 holes. */ -RESERVE_BRK(p2m_populated, PMD_SIZE * 4); + * Some machines can have 3GB I/O holes even. With early_can_reuse_p2m_middle + * it can re-use Xen provided mfn_list array, so we only need to allocate at + * most three P2M top nodes. */ +RESERVE_BRK(p2m_populated, PAGE_SIZE * 3); + static inline unsigned p2m_top_index(unsigned long pfn) { BUG_ON(pfn >= MAX_P2M_PFN); @@ -575,12 +577,99 @@ static bool __init early_alloc_p2m(unsig } return true; } + +/* + * Skim over the P2M tree looking at pages that are either filled with + * INVALID_P2M_ENTRY or with 1:1 PFNs. If found, re-use that page and + * replace the P2M leaf with a p2m_missing or p2m_identity. + * Stick the old page in the new P2M tree location. + */ +bool __init early_can_reuse_p2m_middle(unsigned long set_pfn, unsigned long set_mfn) +{ + unsigned topidx; + unsigned mididx; + unsigned ident_pfns; + unsigned inv_pfns; + unsigned long *p2m; + unsigned long *mid_mfn_p; + unsigned idx; + unsigned long pfn; + + /* We only look when this entails a P2M middle layer */ + if (p2m_index(set_pfn)) + return false; + + for (pfn = 0; pfn <= MAX_DOMAIN_PAGES; pfn += P2M_PER_PAGE) { + topidx = p2m_top_index(pfn); + + if (!p2m_top[topidx]) + continue; + + if (p2m_top[topidx] == p2m_mid_missing) + continue; + + mididx = p2m_mid_index(pfn); + p2m = p2m_top[topidx][mididx]; + if (!p2m) + continue; + + if ((p2m == p2m_missing) || (p2m == p2m_identity)) + continue; + + if ((unsigned long)p2m == INVALID_P2M_ENTRY) + continue; + + ident_pfns = 0; + inv_pfns = 0; + for (idx = 0; idx < P2M_PER_PAGE; idx++) { + /* IDENTITY_PFNs are 1:1 */ + if (p2m[idx] == IDENTITY_FRAME(pfn + idx)) + ident_pfns++; + else if (p2m[idx] == INVALID_P2M_ENTRY) + inv_pfns++; + else + break; + } + if ((ident_pfns == P2M_PER_PAGE) || (inv_pfns == P2M_PER_PAGE)) + goto found; + } + return false; +found: + /* Found one, replace old with p2m_identity or p2m_missing */ + p2m_top[topidx][mididx] = (ident_pfns ? p2m_identity : p2m_missing); + /* And the other for save/restore.. */ + mid_mfn_p = p2m_top_mfn_p[topidx]; + /* NOTE: Even if it is a p2m_identity it should still be point to + * a page filled with INVALID_P2M_ENTRY entries. */ + mid_mfn_p[mididx] = virt_to_mfn(p2m_missing); + + /* Reset where we want to stick the old page in. */ + topidx = p2m_top_index(set_pfn); + mididx = p2m_mid_index(set_pfn); + + /* This shouldn't happen */ + if (WARN_ON(p2m_top[topidx] == p2m_mid_missing)) + early_alloc_p2m(set_pfn); + + if (WARN_ON(p2m_top[topidx][mididx] != p2m_missing)) + return false; + + p2m_init(p2m); + p2m_top[topidx][mididx] = p2m; + mid_mfn_p = p2m_top_mfn_p[topidx]; + mid_mfn_p[mididx] = virt_to_mfn(p2m); + + return true; +} bool __init early_set_phys_to_machine(unsigned long pfn, unsigned long mfn) { if (unlikely(!__set_phys_to_machine(pfn, mfn))) { if (!early_alloc_p2m(pfn)) return false; + if (early_can_reuse_p2m_middle(pfn, mfn)) + return __set_phys_to_machine(pfn, mfn); + if (!early_alloc_p2m_middle(pfn, false /* boundary crossover OK!*/)) return false; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/