From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:50365) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1R1i2E-00021m-Om for qemu-devel@nongnu.org; Thu, 08 Sep 2011 13:05:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1R1i28-00039S-65 for qemu-devel@nongnu.org; Thu, 08 Sep 2011 13:05:06 -0400 Received: from goliath.siemens.de ([192.35.17.28]:28554) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1R1i27-000393-Tq for qemu-devel@nongnu.org; Thu, 08 Sep 2011 13:05:00 -0400 Message-ID: <4E68F5B6.5050909@siemens.com> Date: Thu, 08 Sep 2011 19:04:54 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <1315460008-22657-1-git-send-email-bharata.rao@gmail.com> In-Reply-To: <1315460008-22657-1-git-send-email-bharata.rao@gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2] Fix X86 CPU topology in KVM mode List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "bharata.rao@gmail.com" Cc: "qemu-devel@nongnu.org" , "avi@redhat.com" On 2011-09-08 07:33, bharata.rao@gmail.com wrote: > From: Bharata B Rao > > apic id returned to guest kernel in ebx for cpuid(function=1) depends on > CPUX86State->cpuid_apic_id which gets populated after the cpuid information > is cached in the host kernel. This results in broken CPU topology in guest. > > Fix this by setting cpuid_apic_id before cpuid information is passed to > the host kernel. This is done by moving the setting of cpuid_apic_id > to cpu_x86_init() where it will work for both KVM as well as TCG modes. > > Signed-off-by: Bharata B Rao > --- > This is the next post of the fix that addresses Jan's comment about > bringing back (smp_cpus > 1) check. > > The previous version was posted here: > http://lists.gnu.org/archive/html/qemu-devel/2011-09/msg00892.html > > I coudn't boot a 486 kernel successfully with qemu and hence not > sure if and how this fix breaks i486. Any help from Jan or others > who might have easy means to boot 486 would be good. At least it preserves the current logic, just moves it up in the initialization path. > > hw/pc.c | 1 - > target-i386/helper.c | 5 +++++ > 2 files changed, 5 insertions(+), 1 deletions(-) > > diff --git a/hw/pc.c b/hw/pc.c > index 5bc845a..f9cca4d 100644 > --- a/hw/pc.c > +++ b/hw/pc.c > @@ -933,7 +933,6 @@ static CPUState *pc_new_cpu(const char *cpu_model) > exit(1); > } > if ((env->cpuid_features & CPUID_APIC) || smp_cpus > 1) { > - env->cpuid_apic_id = env->cpu_index; > env->apic_state = apic_init(env, env->cpuid_apic_id); > } > qemu_register_reset(pc_cpu_reset, env); > diff --git a/target-i386/helper.c b/target-i386/helper.c > index 5df40d4..139a193 100644 > --- a/target-i386/helper.c > +++ b/target-i386/helper.c > @@ -1256,6 +1256,11 @@ CPUX86State *cpu_x86_init(const char *cpu_model) > cpu_x86_close(env); > return NULL; > } > + > + if ((env->cpuid_features & CPUID_APIC) || smp_cpus > 1) { > + env->cpuid_apic_id = env->cpu_index; > + } > + > mce_init(env); > > qemu_init_vcpu(env); Tested-and-acked-by: Jan Kiszka Just in time, we happen to hit this bug today too. It confused libvirt in the guest quite a bit... Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux