From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Daniel P. Berrange" Subject: Re: Xen unstable fails to boot from cold on i386 core duo Date: Tue, 18 Dec 2007 00:00:57 +0000 Message-ID: <20071218000057.GD19291@redhat.com> References: <20071217154221.GA32490@redhat.com> Reply-To: "Daniel P. Berrange" Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20071217154221.GA32490@redhat.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On Mon, Dec 17, 2007 at 03:42:21PM +0000, Daniel P. Berrange wrote: > Just testing xen-unstable on some of my machines here. I've got a failure > to boot on a Mac Mini with a i386 Core Duo cpu. > > If I try to boot xen-unstable changeset 16606 from cold it will immediately > crash with this: > > http://people.redhat.com/berrange/xen-3.2.0-fail.jpg > > Sorry for lame camera pic - this being a mac mini there's no serial card, > or even ability to add one in :-( > > If I boot into Xen 3.1.0 it works fine. If I warm-reboot from Xen 3.1.0 > into Xen-unstable changeset 16606 it also works fine. So it seems only the > boot from cold is problematic. > > Attaching the 'xm dmesg' output from a succesfull warm-reboot into > xen-unstable, and the CPU info. > > Any ideas / suggestions ? Converting ff16420d / vmx_cpu_up+0x25d address into a line number with eu-addr2line, it appears as if Xen is crashing & burning in the 'wrmsr' call in the 2nd half of this conditional from arch/x86/hvm/vmx/vmcs.c: if ( eax & IA32_FEATURE_CONTROL_MSR_LOCK ) { if ( !(eax & (IA32_FEATURE_CONTROL_MSR_ENABLE_VMXON_OUTSIDE_SMX | IA32_FEATURE_CONTROL_MSR_ENABLE_VMXON_INSIDE_SMX)) ) { printk("CPU%d: VMX disabled by BIOS.\n", cpu); return 0; } } else { eax = (IA32_FEATURE_CONTROL_MSR_LOCK | IA32_FEATURE_CONTROL_MSR_ENABLE_VMXON_OUTSIDE_SMX | IA32_FEATURE_CONTROL_MSR_ENABLE_VMXON_INSIDE_SMX); wrmsr(IA32_FEATURE_CONTROL_MSR, eax, 0); } In Xen 3.1.0 (which works for me), the 'vmx_cpu_up' method does not exist, but the 'start_vmx' function which does more of less the same thing writes a slightly different msr: if ( eax & IA32_FEATURE_CONTROL_MSR_LOCK ) { if ( (eax & IA32_FEATURE_CONTROL_MSR_ENABLE_VMXON) == 0x0 ) { printk("VMX disabled by Feature Control MSR.\n"); return 0; } } else { wrmsr(IA32_FEATURE_CONTROL_MSR, IA32_FEATURE_CONTROL_MSR_LOCK | IA32_FEATURE_CONTROL_MSR_ENABLE_VMXON, 0); } I guess this explains why Xen-unstable works if I warm re-boot from xen-3.1.0, because the 3.1.0 hypervisor will have already enabled and lock VMX msr. Is it possible that older CPUs / BIOS don't play nice with the extra bit IA32_FEATURE_CONTROL_MSR_ENABLE_VMXON_INSIDE_SMX ...if they don't have SMX support ? Regards, Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|