From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755264Ab3AXTQF (ORCPT ); Thu, 24 Jan 2013 14:16:05 -0500 Received: from terminus.zytor.com ([198.137.202.10]:33417 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755075Ab3AXTQA (ORCPT ); Thu, 24 Jan 2013 14:16:00 -0500 User-Agent: K-9 Mail for Android In-Reply-To: References: <1358990259-22551-1-git-send-email-kys@microsoft.com> <5101035D02000078000B8FFD@nat28.tlf.novell.com> <27092660926e4d3f80394697cc0dc858@SN2PR03MB061.namprd03.prod.outlook.com> <51016C3202000078000B943E@nat28.tlf.novell.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: RE: [PATCH RESEND 1/1] X86: Handle Hyper-V vmbus interrupts as special hypervisor interrupts From: "H. Peter Anvin" Date: Thu, 24 Jan 2013 13:10:15 -0600 To: KY Srinivasan , Jan Beulich CC: "olaf@aepfle.de" , "bp@alien8.de" , "apw@canonical.com" , "x86@kernel.org" , "tglx@linutronix.de" , "devel@linuxdriverproject.org" , "gregkh@linuxfoundation.org" , "jasowang@redhat.com" , "linux-kernel@vger.kernel.org" Message-ID: <52cb66cd-8a8f-461c-adc4-0026afb8c1fd@email.android.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I also have to point out the obvious problem with Xen masquerading as HyperV without implementing the same feature set... KY Srinivasan wrote: > > >> -----Original Message----- >> From: Jan Beulich [mailto:JBeulich@suse.com] >> Sent: Thursday, January 24, 2013 11:16 AM >> To: KY Srinivasan >> Cc: olaf@aepfle.de; bp@alien8.de; apw@canonical.com; x86@kernel.org; >> tglx@linutronix.de; devel@linuxdriverproject.org; >gregkh@linuxfoundation.org; >> jasowang@redhat.com; linux-kernel@vger.kernel.org; hpa@zytor.com >> Subject: RE: [PATCH RESEND 1/1] X86: Handle Hyper-V vmbus interrupts >as >> special hypervisor interrupts >> >> >>> On 24.01.13 at 17:07, KY Srinivasan wrote: >> >> > >> >> -----Original Message----- >> >> From: Jan Beulich [mailto:JBeulich@suse.com] >> >> Sent: Thursday, January 24, 2013 3:48 AM >> >> To: KY Srinivasan >> >> Cc: olaf@aepfle.de; bp@alien8.de; apw@canonical.com; >x86@kernel.org; >> >> tglx@linutronix.de; devel@linuxdriverproject.org; >> > gregkh@linuxfoundation.org; >> >> jasowang@redhat.com; linux-kernel@vger.kernel.org; hpa@zytor.com >> >> Subject: Re: [PATCH RESEND 1/1] X86: Handle Hyper-V vmbus >interrupts as >> >> special hypervisor interrupts >> >> >> >> >>> On 24.01.13 at 02:17, "K. Y. Srinivasan" >wrote: >> >> > @@ -69,6 +74,11 @@ static void __init >ms_hyperv_init_platform(void) >> >> > ms_hyperv.features, ms_hyperv.hints); >> >> > >> >> > clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100); >> >> > + >> >> > + /* >> >> > + * Setup the IDT for hypervisor callback. >> >> > + */ >> >> > + alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR, >> >> hyperv_callback_vector); >> >> >> >> Isn't doing this unconditionally here as problematic as the call >to >> >> clocksource_register_hz() turned out to be when Xen's Hyper-V >> >> shim reacts to the CPUID inquiry above? >> > >> > I was not sure what to make this conditional on at run-time. To the >extent >> > that Xen emulation of Hyper-V is complete, this will be a problem. >Does Xen >> > return all the "feature bits" of Hyper-V. I could discriminate on a >feature >> > that >> > Xen does not plan to emulate. >> >> I've no idea what plans there might be, but that's the code >> there is currently: >> >> int cpuid_viridian_leaves(unsigned int leaf, unsigned int *eax, >> unsigned int *ebx, unsigned int *ecx, >> unsigned int *edx) >> { >> struct domain *d = current->domain; >> >> if ( !is_viridian_domain(d) ) >> return 0; >> >> leaf -= 0x40000000; >> if ( leaf > 6 ) >> return 0; >> >> *eax = *ebx = *ecx = *edx = 0; >> switch ( leaf ) >> { >> case 0: >> *eax = 0x40000006; /* Maximum leaf */ >> *ebx = 0x7263694d; /* Magic numbers */ >> *ecx = 0x666F736F; >> *edx = 0x76482074; >> break; >> case 1: >> *eax = 0x31237648; /* Version number */ >> break; >> case 2: >> /* Hypervisor information, but only if the guest has set its >> own version number. */ >> if ( d->arch.hvm_domain.viridian.guest_os_id.raw == 0 ) >> break; >> *eax = 1; /* Build number */ >> *ebx = (xen_major_version() << 16) | xen_minor_version(); >> *ecx = 0; /* SP */ >> *edx = 0; /* Service branch and number */ >> break; >> case 3: >> /* Which hypervisor MSRs are available to the guest */ >> *eax = (CPUID3A_MSR_APIC_ACCESS | >> CPUID3A_MSR_HYPERCALL | >> CPUID3A_MSR_VP_INDEX); >> break; >> case 4: >> /* Recommended hypercall usage. */ >> if ( (d->arch.hvm_domain.viridian.guest_os_id.raw == 0) || >> (d->arch.hvm_domain.viridian.guest_os_id.fields.os < 4) >) >> break; >> *eax = (CPUID4A_MSR_BASED_APIC | >> CPUID4A_RELAX_TIMER_INT); >> *ebx = 2047; /* long spin count */ >> break; >> } >> >> return 1; >> } >> >> Question is - considering you stated that this is supported >> starting in Win8, doesn't Hyper-V itself announce that >> capability in some explicit way? > >Thanks Jan. Unfortunately I don't think tis interrupt delivery model is >specified via a "feature" bit (I will check with the Windows guys). >Perhaps, we >can have a Hyper-V specific compilation switch to address the Xen >emulation issue. > >Regards, > >K. Y >> >> Jan >> >> -- Sent from my mobile phone. Please excuse brevity and lack of formatting.