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Date: Tue, 8 Jun 2010 17:25:52 +0100 From: Stefano Stabellini <stefano.stabellini@...citrix.com> To: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> CC: Stefano Stabellini <Stefano.Stabellini@...citrix.com>, "jeremy@...p.org" <jeremy@...p.org>, "xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>, "Yaozu (Eddie) Dong" <eddie.dong@...el.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "ddutile@...hat.com" <ddutile@...hat.com>, "sheng@...ux.intel.com" <sheng@...ux.intel.com> Subject: Re: [Xen-devel] [PATCH 02/12] early PV on HVM On Tue, 8 Jun 2010, Konrad Rzeszutek Wilk wrote: > On Tue, Jun 08, 2010 at 04:55:33PM +0100, Stefano Stabellini wrote: > > On Tue, 8 Jun 2010, Konrad Rzeszutek Wilk wrote: > > > > > > + HYPERVISOR_shared_info = (struct shared_info *)shared_info_page; > > > > > > + > > > > > > + /* Don't do the full vcpu_info placement stuff until we have a > > > > > > + possible map and a non-dummy shared_info. */ > > > > > > > > > > Might want to mention where the full vpcu placement is done. > > > > > > > > The comment is not accurate, we actually don't do any vcpu_info > > > > placement on hvm because it is not very useful there. > > > > Better just to remove the comment (I have done so in my tree). > > > > > > > > > > + per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0]; > > > > > > > > So.. what is the purpose of the per_cpu(xen_vcpu, 0) then? > > > > > > > the vcpu info placement memory area is stored in per_cpu(xen_vcpu_info, cpu); > > per_cpu(xen_vcpu, cpu) is just a pointer to that area if it is > > available, otherwise it points to the vcpu_info struct in the shared > > info page. > > I was just wondering why are we doing this when you say: > " don't do any vcpu_info placement on hvm because it is not very useful there." > > So if it is not useful, why do it? > I think Jeremy replied to your question better than me: we still need the vcpu_info stuff for the timer and event channels, but we don't need it to be at a specific address in kernel memory. That is useful only for the following pvops operations: pv_irq_ops.save_fl = __PV_IS_CALLEE_SAVE(xen_save_fl_direct); pv_irq_ops.restore_fl = __PV_IS_CALLEE_SAVE(xen_restore_fl_direct); pv_irq_ops.irq_disable = __PV_IS_CALLEE_SAVE(xen_irq_disable_direct); pv_irq_ops.irq_enable = __PV_IS_CALLEE_SAVE(xen_irq_enable_direct); pv_mmu_ops.read_cr2 = xen_read_cr2_direct; none of which are used in the hvm case. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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