From nobody Mon Feb 9 17:27:25 2026 Delivered-To: importer@patchew.org Received-SPF: none (zohomail.com: 192.237.175.120 is neither permitted nor denied by domain of lists.xenproject.org) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; spf=none (zohomail.com: 192.237.175.120 is neither permitted nor denied by domain of lists.xenproject.org) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=fail(p=none dis=none) header.from=intel.com ARC-Seal: i=1; a=rsa-sha256; t=1579629102; cv=none; d=zohomail.com; s=zohoarc; b=WV3i9WuQ3nhzgvfNEhtsaXeNshq6vr/0gTdcVZpkdMLn28Y6ZtICJc5LxXLlm4tgzveX6lstPJyOVCK0bK0qULOGE2+kI8cj6Pstj9YF8ASy/G0ayNBJ1Ys0Cglvrch/ZDQLba+XdXZN0iyTGMfXcGp55oW4uheFkK6md5z0yW8= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1579629102; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=y0hufSOsgGBD2jGfsRew3urRuK7Yej5zUgKkL645B6Y=; b=LE+B8Bv+pJlakLE4cJECX/9TWM0iakOiO6Ry11dm7tD2G4FxuhLcGzPY9VAK+ddZXSLpcZK9P2yV5QzFLSnAQkM4046U/f7+FHbxMq+mS9uIl0yeOPhQmDFKZ+l/ebCnVUlL3h7p/H7R2QjRfcB+XYQfgjrdcrRyyEBzzInq/Vw= ARC-Authentication-Results: i=1; mx.zohomail.com; spf=none (zohomail.com: 192.237.175.120 is neither permitted nor denied by domain of lists.xenproject.org) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 157962910276919.590209408679698; Tue, 21 Jan 2020 09:51:42 -0800 (PST) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1itxgJ-0005Q4-J2; Tue, 21 Jan 2020 17:51:15 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1itxgH-0005OF-D2 for xen-devel@lists.xenproject.org; Tue, 21 Jan 2020 17:51:13 +0000 Received: from mga04.intel.com (unknown [192.55.52.120]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 7ea87953-3c76-11ea-bb21-12813bfff9fa; Tue, 21 Jan 2020 17:50:21 +0000 (UTC) Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Jan 2020 09:50:11 -0800 Received: from tlengyel-mobl2.amr.corp.intel.com (HELO localhost.localdomain) ([10.251.23.127]) by orsmga006.jf.intel.com with ESMTP; 21 Jan 2020 09:50:10 -0800 X-Inumbo-ID: 7ea87953-3c76-11ea-bb21-12813bfff9fa X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,346,1574150400"; d="scan'208";a="228929277" From: Tamas K Lengyel To: xen-devel@lists.xenproject.org Date: Tue, 21 Jan 2020 09:49:50 -0800 Message-Id: <3afdd6ef6a20236d62942df5958f046a8c3fae9c.1579628566.git.tamas.lengyel@intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: References: MIME-Version: 1.0 Subject: [Xen-devel] [PATCH v5 17/18] 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 , Tamas K Lengyel , Wei Liu , Konrad Rzeszutek Wilk , George Dunlap , Andrew Cooper , Ian Jackson , Stefano Stabellini , Julien Grall , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable 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 mo= re 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 749305417c..c185b0e7c4 100644 --- a/xen/arch/x86/mm/mem_sharing.c +++ b/xen/arch/x86/mm/mem_sharing.c @@ -1611,6 +1611,59 @@ static int mem_sharing_fork(struct domain *d, struct= domain *cd) return rc; } =20 +/* + * The fork reset operation is intended to be used on short-lived forks on= ly. + * There is no hypercall continuation operation implemented for this reaso= n. + * 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 o= ne. + * + * TODO: In case this hypercall would become useful on forks with larger m= emory + * 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 =3D 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 =3D page_to_mfn(page); + + if ( !mfn_valid(mfn) ) + continue; + + gfn =3D mfn_to_gfn(cd, mfn); + mfn =3D __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 =3D 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 =3D 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; @@ -1895,6 +1948,29 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem= _sharing_op_t) arg) break; } =20 + case XENMEM_sharing_op_fork_reset: + { + struct domain *pd; + + rc =3D -EINVAL; + if ( mso.u.fork._pad[0] || mso.u.fork._pad[1] || + mso.u.fork._pad[2] ) + goto out; + + rc =3D -ENOSYS; + if ( !d->parent ) + goto out; + + rc =3D rcu_lock_live_remote_domain_by_id(d->parent->domain_id, &pd= ); + if ( rc ) + goto out; + + rc =3D mem_sharing_fork_reset(pd, d); + + rcu_unlock_domain(pd); + break; + } + default: rc =3D -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 =20 #define XENMEM_SHARING_OP_S_HANDLE_INVALID (-10) #define XENMEM_SHARING_OP_C_HANDLE_INVALID (-9) --=20 2.20.1 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel