Re: [Qemu-devel] [Patch V2 1/2] x86, mce: Basic support to add LMCE support to QEMU
From: Eduardo Habkost
Date: Tue Dec 15 2015 - 10:43:08 EST
On Mon, Dec 14, 2015 at 07:17:27PM -0500, Raj, Ashok wrote:
> On Mon, Dec 14, 2015 at 11:37:16PM +0100, Borislav Petkov wrote:
> > On Mon, Dec 14, 2015 at 02:11:46PM -0500, Raj, Ashok wrote:
> > > This is mostly harmless.. since the MCG_CAP space is shared and has no
> > > conflict between vendors. Also just the CAP being set has no effect.
> > Of course it does - we check SER_P in machine_check_poll() and when
> > I emulate an AMD guest and inject errors into it, error handling is
> > obviously wrong, see:
> > https://lkml.kernel.org/r/20151123150355.GE5134@xxxxxxx
> I can see how this hurts.. since the poller isn't doing cpu model specific
> in the LMCE case, even if you advertise MCG_LMCE_P in MCG_CAP, the guest kernel
> wont call intel_init_lmce() only from mce_intel.c.. so the same problem
> won't happen.
> but the issue Eduardo mentioned seems like the following.
> New QEMU_LMCE + New KVM_LMCE + New_GUEST_LMCE - No problem
> but if you were to migrage the Guest_LMCE to a non-LMCE supported KVM host
> we could run into an issue..
> is this the compatibility issue that you were looking to fix Eduardo?
If I understood you correctly, yes. Also, note that currently
kvm_arch_init_vcpu() simply warns about missing capabilities,
instead of preventing the VM from running/migrating (as it
should). We need to change that, and figure out a good way to
report "feature FOO can't be enabled in this host" errors to
management software. The main problem is that we don't even
have a QMP console available anymore if machine initialization is
CCing libvir-list so they get in the loop.
 This is similar to what we need for CPUID checks, but the new
MCE feature means we need something more generic (that just
reports QOM property names, probably?)
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/