From patchwork Mon Apr 6 15:20:04 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Tamas K Lengyel X-Patchwork-Id: 11475693 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C777E92C for ; Mon, 6 Apr 2020 15:22:06 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id AD1D524899 for ; Mon, 6 Apr 2020 15:22:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AD1D524899 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jLTYH-0006Cg-LR; Mon, 06 Apr 2020 15:20:41 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jLTYG-0006CW-34 for xen-devel@lists.xenproject.org; Mon, 06 Apr 2020 15:20:40 +0000 X-Inumbo-ID: 269a11f0-781a-11ea-b58d-bc764e2007e4 Received: from mga07.intel.com (unknown [134.134.136.100]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 269a11f0-781a-11ea-b58d-bc764e2007e4; Mon, 06 Apr 2020 15:20:30 +0000 (UTC) IronPort-SDR: GhH0YJG6sfeZhz6iYWXyp1Q5S5oWMWFeaBlVhPbu67Kjnwg2F5GZrmcvhPrMiHqkjR5hEK5WHu pPiDi9OR1tvQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Apr 2020 08:20:29 -0700 IronPort-SDR: IGomPIhvUSQNWJQ7dXK23HNYO8qZVxDtB0mJ/W8oKndbVv65oLeSLeKn0pCQbDiDNPk+iMPm15 CVRiYzN44ixw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,351,1580803200"; d="scan'208";a="269107424" Received: from jreyna-mobl.amr.corp.intel.com (HELO localhost.localdomain) ([10.212.25.73]) by orsmga002.jf.intel.com with ESMTP; 06 Apr 2020 08:20:28 -0700 From: Tamas K Lengyel To: xen-devel@lists.xenproject.org Subject: [PATCH v14 2/3] x86/mem_sharing: reset a fork Date: Mon, 6 Apr 2020 08:20:04 -0700 Message-Id: <44e660066f03a39354dbe5d328f30779b8ebc935.1586185752.git.tamas.lengyel@intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: References: MIME-Version: 1.0 X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Tamas K Lengyel , Tamas K Lengyel , Wei Liu , Andrew Cooper , Ian Jackson , George Dunlap , Stefano Stabellini , Jan Beulich , Julien Grall , =?utf-8?q?Roger_Pau_Monn=C3=A9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" Implement hypercall that allows a fork to shed all memory that got allocated for it during its execution and re-load its vCPU context from the parent VM. This allows the forked VM to reset into the same state the parent VM is in a faster way then creating a new fork would be. Measurements show about a 2x speedup during normal fuzzing operations. Performance may vary depending how much memory got allocated for the forked VM. If it has been completely deduplicated from the parent VM then creating a new fork would likely be more performant. Signed-off-by: Tamas K Lengyel Reviewed-by: Roger Pau Monné --- v12: remove continuation & add comment back address style issues pointed out by Jan --- xen/arch/x86/mm/mem_sharing.c | 77 +++++++++++++++++++++++++++++++++++ xen/include/public/memory.h | 1 + 2 files changed, 78 insertions(+) diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c index 64cd706e5a..85951b7bea 100644 --- a/xen/arch/x86/mm/mem_sharing.c +++ b/xen/arch/x86/mm/mem_sharing.c @@ -1749,6 +1749,61 @@ static int fork(struct domain *cd, struct domain *d) return rc; } +/* + * The fork reset operation is intended to be used on short-lived forks only. + * There is no hypercall continuation operation implemented for this reason. + * For forks that obtain a larger memory footprint it is likely going to be + * more performant to create a new fork instead of resetting an existing one. + * + * TODO: In case this hypercall would become useful on forks with larger memory + * footprints the hypercall continuation should be implemented (or if this + * feature needs to be become "stable"). + */ +static int mem_sharing_fork_reset(struct domain *d, struct domain *pd) +{ + int rc; + struct p2m_domain *p2m = p2m_get_hostp2m(d); + struct page_info *page, *tmp; + + domain_pause(d); + + /* need recursive lock because we will free pages */ + spin_lock_recursive(&d->page_alloc_lock); + page_list_for_each_safe(page, tmp, &d->page_list) + { + p2m_type_t p2mt; + p2m_access_t p2ma; + mfn_t mfn = page_to_mfn(page); + gfn_t gfn = mfn_to_gfn(d, mfn); + + mfn = __get_gfn_type_access(p2m, gfn_x(gfn), &p2mt, &p2ma, + 0, NULL, false); + + /* only reset pages that are sharable */ + if ( !p2m_is_sharable(p2mt) ) + continue; + + /* take an extra reference or just skip if can't for whatever reason */ + if ( !get_page(page, d) ) + continue; + + /* forked memory is 4k, not splitting large pages so this must work */ + rc = p2m->set_entry(p2m, gfn, INVALID_MFN, PAGE_ORDER_4K, + p2m_invalid, p2m_access_rwx, -1); + ASSERT(!rc); + + put_page_alloc_ref(page); + put_page(page); + } + spin_unlock_recursive(&d->page_alloc_lock); + + rc = copy_settings(d, pd); + + domain_unpause(d); + + return rc; +} + int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg) { int rc; @@ -2039,6 +2094,28 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg) break; } + case XENMEM_sharing_op_fork_reset: + { + struct domain *pd; + + rc = -EINVAL; + if ( mso.u.fork.pad[0] || mso.u.fork.pad[1] || mso.u.fork.pad[2] ) + goto out; + + rc = -ENOSYS; + if ( !d->parent ) + goto out; + + rc = rcu_lock_live_remote_domain_by_id(d->parent->domain_id, &pd); + if ( rc ) + goto out; + + rc = mem_sharing_fork_reset(d, pd); + + rcu_unlock_domain(pd); + break; + } + default: rc = -ENOSYS; break; diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h index 5ee4e0da12..d36d64b8dc 100644 --- a/xen/include/public/memory.h +++ b/xen/include/public/memory.h @@ -483,6 +483,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_mem_access_op_t); #define XENMEM_sharing_op_audit 7 #define XENMEM_sharing_op_range_share 8 #define XENMEM_sharing_op_fork 9 +#define XENMEM_sharing_op_fork_reset 10 #define XENMEM_SHARING_OP_S_HANDLE_INVALID (-10) #define XENMEM_SHARING_OP_C_HANDLE_INVALID (-9)