On Thu, Sep 07, 2017 at 01:05:33AM +0000, Gonglei (Arei) wrote: > > > > -----Original Message----- > > From: Eduardo Habkost [mailto:ehabk...@redhat.com] > > Sent: Tuesday, September 05, 2017 9:17 PM > > To: Gonglei (Arei) > > Cc: qemu-devel@nongnu.org; m...@redhat.com; pbonz...@redhat.com; > > r...@twiddle.net; mtosa...@redhat.com; vroze...@redhat.com; > > Huangweidong (C) > > Subject: Re: [PATCH 2/2] i386/cpu/hyperv: support over 64 vcpus for windows > > guests > > > > On Tue, Sep 05, 2017 at 05:30:05PM +0800, Gonglei wrote: > > > Starting with Windows Server 2012 and Windows 8, if > > > CPUID.40000005.EAX contains a value of -1, Windows assumes specific > > > limit to the number of VPs. In this case, Windows Server 2012 > > > guest VMs may use more than 64 VPs, up to the maximum supported > > > number of processors applicable to the specific Windows > > > version being used. > > > > > > > > https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/referenc > > e/tlfs > > > > > > For compatibility, Let's introduce a new property for X86CPU, > > > named "hv-cpuid-limits-eax" as Paolo's suggestion, and set it > > > to "on" before machine 2.10. > > > > > > Signed-off-by: Gonglei <arei.gong...@huawei.com> > > > --- > > > include/hw/i386/pc.h | 5 +++++ > > > target/i386/cpu.c | 1 + > > > target/i386/cpu.h | 2 ++ > > > target/i386/kvm.c | 18 +++++++++++++++++- > > > 4 files changed, 25 insertions(+), 1 deletion(-) > > > > > > diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h > > > index 8226904..db32e58 100644 > > > --- a/include/hw/i386/pc.h > > > +++ b/include/hw/i386/pc.h > > > @@ -371,6 +371,11 @@ bool e820_get_entry(int, uint32_t, uint64_t *, > > uint64_t *); > > > > > > #define PC_COMPAT_2_10 \ > > > HW_COMPAT_2_10 \ > > > + {\ > > > + .driver = TYPE_X86_CPU,\ > > > + .property = "hv_cpuid_limits_eax",\ > > > > The property name is hv-cpuid-limits-eax. > > > Make sense to me. > > > > + .value = "on",\ > > > + },\ > > > > > > #define PC_COMPAT_2_9 \ > > > HW_COMPAT_2_9 \ > > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c > > > index 69676e1..0d47bdd 100644 > > > --- a/target/i386/cpu.c > > > +++ b/target/i386/cpu.c > > > @@ -4145,6 +4145,7 @@ static Property x86_cpu_properties[] = { > > > false), > > > DEFINE_PROP_BOOL("vmware-cpuid-freq", X86CPU, > > vmware_cpuid_freq, true), > > > DEFINE_PROP_BOOL("tcg-cpuid", X86CPU, expose_tcg, true), > > > + DEFINE_PROP_BOOL("hv-cpuid-limits-eax", X86CPU, > > hv_cpuid_limits_eax, false), > > > > The property name "hv-cpuid-limits-eax" doesn't say anything > > about what it does exactly when set to true. > > > > What about just making it int32? e.g.: > > > > DEFINE_PROP_INT32("x-hv-max-vps", X86CPU, hv_max_vps, -1) > > [...] > > {\ > > .driver = TYPE_X86_CPU,\ > > .property = "x-hv-max-vps",\ > > .value = "0x40",\ > > },\ > > [...] > > c->function = HYPERV_CPUID_IMPLEMENT_LIMITS; > > c->eax = cpu->hv_max_vps; > > > > > > (The "x-" prefix indicates that the property is not supposed to > > be a stable user interface.) > > > I thought about this as well. > but actually we can't assure that users set the x-hv-max-vps an invalid value > if > we use this method. Do we really need to expose eax directly?
We don't really need to expose eax directly and I'm not against a boolean property, but I think an integer property with the actual CPUID value makes the compat code simpler and the purpose of the entry at PC_COMPAT_* more obvious. Properties prefixed with "x-" are for internal QEMU usage or debugging, if users want to fiddle with it, they do it at their own risk. I don't see a problem with that. > > > > > > DEFINE_PROP_END_OF_LIST() > > > }; > > > > > > diff --git a/target/i386/cpu.h b/target/i386/cpu.h > > > index 525d35d..f8b455a 100644 > > > --- a/target/i386/cpu.h > > > +++ b/target/i386/cpu.h > > > @@ -1282,6 +1282,8 @@ struct X86CPU { > > > int32_t socket_id; > > > int32_t core_id; > > > int32_t thread_id; > > > + > > > + bool hv_cpuid_limits_eax; > > > }; > > > > > > static inline X86CPU *x86_env_get_cpu(CPUX86State *env) > > > diff --git a/target/i386/kvm.c b/target/i386/kvm.c > > > index 6db7783..cf6ef96 100644 > > > --- a/target/i386/kvm.c > > > +++ b/target/i386/kvm.c > > > @@ -751,7 +751,23 @@ int kvm_arch_init_vcpu(CPUState *cs) > > > > > > c = &cpuid_data.entries[cpuid_i++]; > > > c->function = HYPERV_CPUID_IMPLEMENT_LIMITS; > > > - c->eax = 0x40; > > > + > > > + if (!cpu->hv_cpuid_limits_eax) { > > > + /* > > > + * Starting with Windows Server 2012 and Windows 8, if > > > + * CPUID.40000005.EAX contains a value of -1, Windows > > > + * assumes specific limit to the number of VPs. In this case, > > > + * Windows Server 2012 guest VMs may use more than 64 > > VPs, > > > + * up to the maximum supported number of processors > > > + * applicable to the specific Windows version being used. > > > > That was a direct quote from a document, so I recommend citing > > the specific document you quoted. e.g.: > > > > /* > > * From "Requirements for Implementing the Microsoft > > * Hypervisor Interface": > > * > > https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/referenc > > e/tlfs > > * > > * "Starting with Windows Server 2012 and Windows 8, if > > * CPUID.40000005.EAX contains a value of -1, Windows assumes > > * specific limit to the number of VPs. In this case, Windows > > * Server 2012 guest VMs may use more than 64 VPs, up to the > > * maximum supported number of processors applicable to the > > * specific Windows version being used." > > */ > > > > > > > + * > > > + * https://docs.microsoft.com/en-us/virtualization/ > > > + * hyper-v-on-windows/reference/tlfs > > > > IMO a long line is preferable to a broken URL. > > > Make sense to me. > > Thanks, > -Gonglei > -- Eduardo