Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753734Ab3EFNFN (ORCPT ); Mon, 6 May 2013 09:05:13 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:23870 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753090Ab3EFNFH (ORCPT ); Mon, 6 May 2013 09:05:07 -0400 From: Konrad Rzeszutek Wilk To: linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, stefano.stabellini@eu.citrix.com Cc: Konrad Rzeszutek Wilk Subject: [PATCH 2/4] xen/vcpu: Document the xen_vcpu_info and xen_vcpu Date: Mon, 6 May 2013 09:04:56 -0400 Message-Id: <1367845498-14290-3-git-send-email-konrad.wilk@oracle.com> X-Mailer: git-send-email 1.8.1.4 In-Reply-To: <1367845498-14290-1-git-send-email-konrad.wilk@oracle.com> References: <1367845498-14290-1-git-send-email-konrad.wilk@oracle.com> X-Source-IP: ucsinet21.oracle.com [156.151.31.93] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2301 Lines: 61 They are important structures and it is not clear at first look what they are for. The xen_vcpu is a pointer. By default it points to the shared_info structure (at the CPU offset location). However if the VCPUOP_register_vcpu_info hypercall is implemented we can make the xen_vcpu pointer point to a per-CPU location. Signed-off-by: Konrad Rzeszutek Wilk --- arch/x86/xen/enlighten.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index 94a81f4..9b34475 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -85,7 +85,21 @@ EXPORT_SYMBOL_GPL(hypercall_page); +/* + * Pointer to the xen_vcpu_info structure or + * &HYPERVISOR_shared_info->vcpu_info[cpu]. See xen_hvm_init_shared_info + * and xen_vcpu_setup for details. By default it points to share_info->vcpu_info + * but if the hypervisor supports VCPUOP_register_vcpu_info then it can point + * to xen_vcpu_info. The pointer is used in __xen_evtchn_do_upcall to + * acknowledge pending events. + */ DEFINE_PER_CPU(struct vcpu_info *, xen_vcpu); + +/* + * Per CPU pages used if hypervisor supports VCPUOP_register_vcpu_info + * hypercall. This can be used both in PV and PVHVM mode. The structure + * overrides the default per_cpu(xen_vcpu, cpu) value. + */ DEFINE_PER_CPU(struct vcpu_info, xen_vcpu_info); enum xen_domain_type xen_domain_type = XEN_NATIVE; @@ -187,7 +201,12 @@ static void xen_vcpu_setup(int cpu) /* Check to see if the hypervisor will put the vcpu_info structure where we want it, which allows direct access via - a percpu-variable. */ + a percpu-variable. + N.B. This hypercall can _only_ be called once per CPU. Subsequent + calls will error out with -EINVAL. This is due to the fact that + hypervisor has no unregister variant and this hypercall does not + allow to over-write info.mfn and info.offset. + */ err = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, cpu, &info); if (err) { -- 1.8.1.4 -- 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/