linux-kernel - Re: [PATCH v12 rebased] kvm: notify host when the guest is panicked

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Date:	Sun, 3 Mar 2013 19:29:53 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Gleb Natapov <gleb@...hat.com>
Cc:	Hu Tao <hutao@...fujitsu.com>, kvm list <kvm@...r.kernel.org>,
	qemu-devel <qemu-devel@...gnu.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Daniel P. Berrange" <berrange@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Blue Swirl <blauwirbel@...il.com>,
	Eric Blake <eblake@...hat.com>,
	Andrew Jones <drjones@...hat.com>,
	Sasha Levin <levinsasha928@...il.com>,
	Luiz Capitulino <lcapitulino@...hat.com>,
	Wen Congyang <wency@...fujitsu.com>
Subject: Re: [PATCH v12 rebased] kvm: notify host when the guest is panicked

On Sun, Mar 03, 2013 at 03:00:22PM +0200, Gleb Natapov wrote:
> 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.

KVM guest <-> KVM host interface is not dependent on ACPI, so far. Say,
its possible to use a Linux guest without ACPI and have KVM paravirt 
fully functional.

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