From patchwork Mon Jan 27 18:06:36 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tamas K Lengyel X-Patchwork-Id: 11353131 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 4CEEC112B for ; Mon, 27 Jan 2020 18:35:35 +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 3225424681 for ; Mon, 27 Jan 2020 18:35:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3225424681 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none 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 1iw9Dl-0002Jk-CA; Mon, 27 Jan 2020 18:34:49 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1iw9Dk-0002Iq-4E for xen-devel@lists.xenproject.org; Mon, 27 Jan 2020 18:34:48 +0000 X-Inumbo-ID: a0644668-4133-11ea-b45d-bc764e2007e4 Received: from mga07.intel.com (unknown [134.134.136.100]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id a0644668-4133-11ea-b45d-bc764e2007e4; Mon, 27 Jan 2020 18:34:17 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Jan 2020 10:06:50 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,370,1574150400"; d="scan'208";a="231562399" Received: from tlengyel-mobl2.amr.corp.intel.com (HELO localhost.localdomain) ([10.254.183.124]) by orsmga006.jf.intel.com with ESMTP; 27 Jan 2020 10:06:49 -0800 From: Tamas K Lengyel To: xen-devel@lists.xenproject.org Date: Mon, 27 Jan 2020 10:06:36 -0800 Message-Id: X-Mailer: git-send-email 2.20.1 In-Reply-To: References: MIME-Version: 1.0 Subject: [Xen-devel] [PATCH v6 8/9] x86/mem_sharing: reset a fork 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 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 --- xen/arch/x86/mm/mem_sharing.c | 76 +++++++++++++++++++++++++++++++++++ xen/include/public/memory.h | 1 + 2 files changed, 77 insertions(+) diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c index b6be78486d..88549db7b2 100644 --- a/xen/arch/x86/mm/mem_sharing.c +++ b/xen/arch/x86/mm/mem_sharing.c @@ -1613,6 +1613,59 @@ static int mem_sharing_fork(struct domain *d, struct domain *cd) 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. + */ +static int mem_sharing_fork_reset(struct domain *d, struct domain *cd) +{ + int rc; + struct p2m_domain* p2m = p2m_get_hostp2m(cd); + struct page_info *page, *tmp; + + domain_pause(cd); + + page_list_for_each_safe(page, tmp, &cd->page_list) + { + p2m_type_t p2mt; + p2m_access_t p2ma; + gfn_t gfn; + mfn_t mfn = page_to_mfn(page); + + if ( !mfn_valid(mfn) ) + continue; + + gfn = mfn_to_gfn(cd, mfn); + mfn = __get_gfn_type_access(p2m, gfn_x(gfn), &p2mt, &p2ma, + 0, NULL, false); + + if ( !p2m_is_ram(p2mt) || p2m_is_shared(p2mt) ) + continue; + + /* take an extra reference */ + if ( !get_page(page, cd) ) + continue; + + 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); + } + + if ( !(rc = hvm_copy_context_and_params(d, cd)) ) + fork_tsc(d, cd); + + domain_unpause(cd); + return rc; +} + int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg) { int rc; @@ -1897,6 +1950,29 @@ 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(pd, d); + + rcu_unlock_domain(pd); + break; + } + default: rc = -ENOSYS; break; diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h index 90a3f4498e..e3d063e22e 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)