From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mukesh Rathor Subject: Re: [PATCH RFC] pvh: clearly specify used parameters in vcpu_guest_context Date: Fri, 15 Nov 2013 17:12:27 -0800 Message-ID: <20131115171227.5c2797d2@mantra.us.oracle.com> References: <1384530622-31703-1-git-send-email-roger.pau@citrix.com> <52865AC60200007800103AAE@nat28.tlf.novell.com> <52864E97.9020402@eu.citrix.com> <52865DCB0200007800103AD8@nat28.tlf.novell.com> <20131115135654.52e52bd4@mantra.us.oracle.com> <20131115155652.3201414a@mantra.us.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1VhUSB-0005G1-OR for xen-devel@lists.xenproject.org; Sat, 16 Nov 2013 01:13:40 +0000 In-Reply-To: <20131115155652.3201414a@mantra.us.oracle.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Mukesh Rathor Cc: Keir Fraser , George Dunlap , Tim Deegan , Jan Beulich , xen-devel@lists.xenproject.org, Roger Pau Monne List-Id: xen-devel@lists.xenproject.org On Fri, 15 Nov 2013 15:56:52 -0800 Mukesh Rathor wrote: > On Fri, 15 Nov 2013 13:56:54 -0800 > Mukesh Rathor wrote: > > > On Fri, 15 Nov 2013 16:45:47 +0000 > > "Jan Beulich" wrote: > > ........ > > > > We had talked about this while ago, but upon boot, the first thing > > a vcpu needs is access to kernel data structure. (A secondary vcpu > > is bootstrapped way up into the kernel). It would be possible to > > get rid of gs_base_kernel, but will take some work on the linux > > side. I can try and test it out, and let you guys know. > > Ok, looking at this more, I can hack cpu_bringup_and_idle() in > linux to include a static variable for cpuid, which is the least a > vcpu needs to know first thing. But, I think that would not work when > vcpu hotplug support is added. Another option would be to pass cpuid > in one of the registers, say rdi. Thus, rdi == cpuid will be passed > to VCPUOP_initialise. In bringup function, the booting vcpu can then > load it's own gs based on the cpuid. If linux folks, konrad (CCd), is > OK with this, we can remove gs_base_kernel. Otherwise, it's such a > small thing, hopefually it can stay. Konrad, Here's the changes needed on linux side to remove gs_base_kernel. Since, I imagine vcpu hotplug would go thru the same path, it would work there also. If this looks OK to everybody, we can remove gs_base_kernel from the VCPUOP_initialise call. thanks, Mukesh diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c index aa89bbf..54d1022 100644 --- a/arch/x86/xen/smp.c +++ b/arch/x86/xen/smp.c @@ -99,14 +99,8 @@ static void cpu_bringup(void) wmb(); /* make sure everything is out */ } -/* - * The vcpu is coming up with only gs_base_kernel set so we can do - * smp_processor_id() here. We need to set the rest of the context first thing. - */ -static void pvh_set_bringup_context(void) +static void pvh_set_bringup_context(int cpu) { - int cpu = smp_processor_id(); - load_percpu_segment(cpu); switch_to_new_gdt(smp_processor_id()); @@ -121,11 +115,12 @@ static void pvh_set_bringup_context(void) : : "r" (__KERNEL_DS), "a" (__KERNEL_CS) : "memory"); } -static void cpu_bringup_and_idle(void) +/* Note: cpu parameter is only relevant for PVH */ +static void cpu_bringup_and_idle(int cpu) { if (xen_feature(XENFEAT_auto_translated_physmap) && xen_feature(XENFEAT_supervisor_mode_kernel)) - pvh_set_bringup_context(); + pvh_set_bringup_context(cpu); cpu_bringup(); cpu_startup_entry(CPUHP_ONLINE); @@ -393,8 +388,6 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle) /* Note: PVH is not yet supported on x86_32. */ ctxt->user_regs.fs = __KERNEL_PERCPU; ctxt->user_regs.gs = __KERNEL_STACK_CANARY; -#else - ctxt->gs_base_kernel = per_cpu_offset(cpu); #endif ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle; @@ -426,6 +419,8 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle) #ifdef CONFIG_X86_32 ctxt->event_callback_cs = __KERNEL_CS; ctxt->failsafe_callback_cs = __KERNEL_CS; +#else + ctxt->gs_base_kernel = per_cpu_offset(cpu); #endif ctxt->event_callback_eip = (unsigned long)xen_hypervisor_callback; @@ -433,7 +428,8 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle) (unsigned long)xen_failsafe_callback; ctxt->user_regs.cs = __KERNEL_CS; per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir); - } + } else + ctxt->user_regs.rdi = cpu; ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs); ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));