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Date: Sun, 3 Mar 2013 15:00:22 +0200
From: Gleb Natapov <gleb@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Hu Tao <hutao@cn.fujitsu.com>, kvm list <kvm@vger.kernel.org>,
        qemu-devel <qemu-devel@nongnu.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Daniel P. Berrange" <berrange@redhat.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Jan Kiszka <jan.kiszka@siemens.com>, Blue Swirl <blauwirbel@gmail.com>,
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        Sasha Levin <levinsasha928@gmail.com>,
        Luiz Capitulino <lcapitulino@redhat.com>,
        Wen Congyang <wency@cn.fujitsu.com>
Subject: Re: [PATCH v12 rebased] kvm: notify host when the guest is panicked
Message-ID: <20130303130022.GF23616@redhat.com>
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On Fri, Mar 01, 2013 at 09:03:12PM -0300, Marcelo Tosatti wrote:
> On Thu, Feb 28, 2013 at 04:54:25PM +0800, Hu Tao wrote:
> > > > diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
> > > > index 06fdbd9..c15ef33 100644
> > > > --- a/arch/x86/include/uapi/asm/kvm_para.h
> > > > +++ b/arch/x86/include/uapi/asm/kvm_para.h
> > > > @@ -96,5 +96,7 @@ struct kvm_vcpu_pv_apf_data {
> > > >  #define KVM_PV_EOI_ENABLED KVM_PV_EOI_MASK
> > > >  #define KVM_PV_EOI_DISABLED 0x0
> > > >  
> > > > +#define KVM_PV_EVENT_PORT	(0x505UL)
> > > > +
> > > 
> > > No need for the ioport to be hard coded. What are the options to
> > > communicate an address to the guest? An MSR, via ACPI?
> > 
> > I'm not quite understanding here. By 'address', you mean an ioport?
> > how to communicate an address? (I have little knowledge about ACPI)
> 
> Yes, the ioport. The address of the ioport should not be fixed (for
> example future emulated board could use that fixed ioport address,
> 0x505UL).
> 
> One option is to pass the address via an MSR. Yes, that is probably the
> best option because there is no dependency on ACPI.
> 
Why dependency on ACPI is problematic? ACPI is the standard way on x86
to enumerate platform devices. Passing it through MSR makes this panic
device CPU interface which it is not. And since relying on #GP to detect
valid MSRs is not good interface we will have to guard it by cpuid bit.

--
			Gleb.