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 15:56:52 -0800 Message-ID: <20131115155652.3201414a@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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1VhTH3-0004Tu-Km for xen-devel@lists.xenproject.org; Fri, 15 Nov 2013 23:58:05 +0000 In-Reply-To: <20131115135654.52e52bd4@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 13:56:54 -0800 Mukesh Rathor wrote: > On Fri, 15 Nov 2013 16:45:47 +0000 > "Jan Beulich" wrote: > > > >>> On 15.11.13 at 17:40, George Dunlap > > >>> wrote: > > > On 15/11/13 16:32, Jan Beulich wrote: > > >>>>> On 15.11.13 at 16:50, Roger Pau Monne > > >>>>> wrote: > > >>> --- a/xen/arch/x86/domain.c > > >>> +++ b/xen/arch/x86/domain.c > > >>> @@ -704,9 +704,11 @@ int arch_set_info_guest( > > >>> /* PVH 32bitfixme */ > > >>> ASSERT(!compat); > > >>> > > >>> - if ( c(ctrlreg[1]) || c(ldt_base) || c(ldt_ents) || > > >>> + if ( c(ctrlreg[0]) || c(ctrlreg[1]) || c(ctrlreg[2]) || > > >>> + c(ctrlreg[4]) || c(ldt_base) || c(ldt_ents) || > > >> I think it should actually be a bug for the guest to request an > > >> all blank CR0 or CR4. Minimally CR0.PE, CR0.PG, and CR4.PAE > > >> would seem to be a valid requirement to be set. > > >> > > >> Apart from that ctrlreg[] is an 8-element array... And I don't > > >> see debugreg[] being verified at all. > > >> > > >>> c(user_regs.cs) || c(user_regs.ss) || > > >>> c(user_regs.es) || c(user_regs.ds) || c(user_regs.fs) || > > >>> c(user_regs.gs) || > > >>> + c(kernel_ss) || c(kernel_sp) || > > >>> c.nat->gs_base_kernel || > > >> So George and/or Mukesh found it necessary to set > > >> gs_base_kernel, and you rip it out? I'm curious as to what > > >> they're going to say... > > > > > > I didn't find it necessary; I was mostly focused on merging the > > > PVH and HVM codepaths without causing any regressions. It's not > > > obvious to me what's special about gs_base_kernel, and I haven't > > > yet gone back to try to find out why Mukesh did it that way. > > Hi, > > 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. thanks, Mukesh