Subject: Re: [PATCH -v2] Add MCE support to KVM
From: Huang Ying <ying.huang@intel.com>
To: Kyle Moffett <kyle@moffetthome.net>
Cc: Anthony Liguori <anthony@codemonkey.ws>, Avi Kivity <avi@redhat.com>,
       "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       Andi Kleen <andi@firstfloor.org>
In-Reply-To: <f73f7ab80904192057q3d918ceco81c09febb493e1c3@mail.gmail.com>
References: <1239953345.6842.3.camel@yhuang-dev.sh.intel.com>
	 <49E9F7BE.4090904@codemonkey.ws>
	 <1240190385.6842.45.camel@yhuang-dev.sh.intel.com>
	 <f73f7ab80904192057q3d918ceco81c09febb493e1c3@mail.gmail.com>
Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-qpEfS5U8554ADCqBAjig"
Date: Mon, 20 Apr 2009 13:04:31 +0800
Message-Id: <1240203871.6842.54.camel@yhuang-dev.sh.intel.com>
Mime-Version: 1.0
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2614
Lines: 65


--=-qpEfS5U8554ADCqBAjig
Content-Type: text/plain
Content-Transfer-Encoding: quoted-printable

On Mon, 2009-04-20 at 11:57 +0800, Kyle Moffett wrote:
> On Sun, Apr 19, 2009 at 9:19 PM, Huang Ying <ying.huang@intel.com> wrote:
> > 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 a=
re
> >> > 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.
>=20
> 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.

Yes. Puting this in kernel-space would make it more reliable to forward
the MCE to KVM guest.

Best Regards,
Huang Ying

--=-qpEfS5U8554ADCqBAjig
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: This is a digitally signed message part

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (GNU/Linux)

iEYEABECAAYFAknsAlsACgkQKhFGF+eHlpiXSACgoqTBnfiWROCMhHva7KCijbSY
qDYAnRMWITsVcDpB+aVtNPaDaJ/AQhgo
=PujK
-----END PGP SIGNATURE-----

--=-qpEfS5U8554ADCqBAjig--

--
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/