Message-ID: <49EDF057.9060501@codemonkey.ws>
Date: Tue, 21 Apr 2009 11:12:07 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
User-Agent: Thunderbird 2.0.0.21 (X11/20090320)
MIME-Version: 1.0
To: Avi Kivity <avi@redhat.com>
CC: Huang Ying <ying.huang@intel.com>, kvm@vger.kernel.org,
       linux-kernel@vger.kernel.org, Andi Kleen <andi@firstfloor.org>
Subject: Re: [PATCH -v2] Add MCE support to KVM
References: <1239953345.6842.3.camel@yhuang-dev.sh.intel.com> <49E9F7BE.4090904@codemonkey.ws> <49EAE334.9020803@redhat.com>
In-Reply-To: <49EAE334.9020803@redhat.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1503
Lines: 37

Avi Kivity wrote:
> 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.
>>
>
> You also need to inject the MCE.

Regardless of the KVM interface for this, to go upstream to QEMU, this 
needs a TCG implementation which means the logic must be duplicated in 
userspace.  In particular, this is because a user-visible command is 
being introduced in the monitor.

So Avi, regardless of what interface is chosen for KVM, can you hold off 
applying these patches until there is a TCG implementation?  Otherwise, 
we'll be playing catchup between kvm-userspace and upstream QEMU forever.

Regards,

Anthony Liguori

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/