linux-kernel - Re: [PATCH 11/16] KVM: TDX: Always block INIT/SIPI

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Message-ID: <de52a2dbdcf844483cbc7aef03ffde1d7bc030d9.camel@intel.com>
Date: Thu, 9 Jan 2025 02:46:51 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "seanjc@...gle.com" <seanjc@...gle.com>, "binbin.wu@...ux.intel.com"
	<binbin.wu@...ux.intel.com>
CC: "Gao, Chao" <chao.gao@...el.com>, "Edgecombe, Rick P"
	<rick.p.edgecombe@...el.com>, "Li, Xiaoyao" <xiaoyao.li@...el.com>, "Chatre,
 Reinette" <reinette.chatre@...el.com>, "Hunter, Adrian"
	<adrian.hunter@...el.com>, "tony.lindgren@...ux.intel.com"
	<tony.lindgren@...ux.intel.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "Yamahata, Isaku"
	<isaku.yamahata@...el.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "Zhao, Yan Y" <yan.y.zhao@...el.com>
Subject: Re: [PATCH 11/16] KVM: TDX: Always block INIT/SIPI

On Thu, 2025-01-09 at 10:26 +0800, Binbin Wu wrote:
> > > > I think we can just say TDX doesn't support vcpu reset no matter due to
> > > > INIT event or not.
> > That's not entirely accurate either though.  TDX does support KVM's version of
> > RESET, because KVM's RESET is "power-on", i.e. vCPU creation.  Emulation of
> > runtime RESET is userspace's responsibility.
> > 
> > The real reason why KVM doesn't do anything during KVM's RESET is that what
> > little setup KVM does/can do needs to be defered until after guest CPUID is
> > configured.
> > 
> > KVM should also WARN if a TDX vCPU gets INIT, no?
> 
> There was a KVM_BUG_ON() if a TDX vCPU gets INIT in v19, and later it was
> removed during the cleanup about removing WARN_ON_ONCE() and KVM_BUG_ON().
> 
> Since INIT/SIPI are always blocked for TDX guests, a delivery of INIT
> event is a KVM bug and a WARN_ON_ONCE() is appropriate for this case.

Can TDX guest issue INIT via IPI?  Perhaps KVM_BUG_ON() is safer?