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

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Message-ID: <20090420053040.GT14687@one.firstfloor.org>
Date:	Mon, 20 Apr 2009 07:30:40 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Kyle Moffett <kyle@...fetthome.net>
Cc:	Huang Ying <ying.huang@...el.com>,
	Anthony Liguori <anthony@...emonkey.ws>,
	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

> IMO the main reason to put this in kernel-space would be to make it
> possible to automatically forward some MCE errors generated by the
> real hardware (RAM ECC errors for example) down into the VM.  Right
> now I suppose you could do that with the patches to forward RAM-based
> hard MCEs to userspace using SIGSEGV and handling the SIGSEGV in
> userspace, but that seems more fragile to me.

I think you refer to my hwpoison patches that generate SIGBUS?

The event has to go through user space anyways. The code to generate
the fake MCE from the SIGBUS is (or rather will be with current
patch) in qemu. Normally the principle to process such errors
as quickly as possible is sound though, although I'm not sure
how much difference it makes. In theory it could be put
into kernel too, but you would need a "in kernel signal handler"
then, which would need quite some more changes.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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