linux-kernel - Re: [PATCH -v2] Add MCE support to KVM

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Date:	Mon, 20 Apr 2009 09:19:45 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	Anthony Liguori <anthony@...emonkey.ws>
Cc:	Avi Kivity <avi@...hat.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH -v2] Add MCE support to KVM

On Sat, 2009-04-18 at 23:54 +0800, Anthony Liguori wrote:
> Huang Ying wrote:
> > The related MSRs are emulated. MCE capability is exported via
> > extension KVM_CAP_MCE and ioctl KVM_X86_GET_MCE_CAP_SUPPORTED. A new
> > vcpu ioctl command KVM_X86_SETUP_MCE is used to setup MCE emulation
> > such as the mcg_cap. MCE is injected via vcpu ioctl command
> > KVM_X86_SET_MCE. Extended machine-check state (MCG_EXT_P) and CMCI are
> > not simulated.
> >   
> 
> Maybe I'm missing something, but couldn't this be implemented entirely 
> within userspace?  There's nothing VT/SVM specific about this.  If the 
> issue is setting these MSRs from userspace via KVM_SET_MSRS isn't 
> enough, perhaps we should add userspace MSR handling.
> 
> Also, if you implement the MSR logic in userspace, it's pretty simple to 
> make it work in the non-TCG case which will be a requirement for 
> upstream merging.

There is more logic than just KVM_SET_MSRS, such as BANK reporting
disabling, overwriting rules, triple fault for UC MCE during MCIP.
Although these logic can be implemented in user space, I think put them
in kernel space is easy to be understood. And the code is pretty short.

Best Regards,
Huang Ying


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