From: Gleb Natapov <gleb@redhat.com>
To: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Vivek Goyal <vgoyal@redhat.com>,
linux-kernel@vger.kernel.org,
Suresh Siddha <suresh.b.siddha@intel.com>,
Sheng Yang <sheng@linux.intel.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"avi@redhat.com" <avi@redhat.com>
Subject: Re: [PATCH v4] enable x2APIC without interrupt remapping under KVM
Date: Tue, 30 Jun 2009 21:53:48 +0300 [thread overview]
Message-ID: <20090630185347.GD8122@redhat.com> (raw)
In-Reply-To: <86802c440906301143s14d0cc9ej9b666271a1ce15ba@mail.gmail.com>
On Tue, Jun 30, 2009 at 11:43:41AM -0700, Yinghai Lu wrote:
> 2009/6/30 Gleb Natapov <gleb@redhat.com>:
>
> >>
> >> how about kexec second kernel in KVM ?
> >>
> >> x2apic_preenabled will be set in second kernel.
> >>
> > Yes, bummer. But the similar problem exist now and without KVM. After
> > running x2apic enabled kernel you can't kexec kernel without x2apic
> > support.
>
> if the first kernel enable x2apic and intr_remapping, and second
> kernel has x2apic and intr_remap support.
> we can kexec the second kernel.
>
And if it hasn't we cannot, that is what I am trying to point out.
> restoring to original state is not possible for kdump case.
>
Shouldn't it be enough to run UP kernel for kdump? So kdump can reset BSP
apic to xAPIC mode before starting a kernel with maxcpus=1.
> maybe with minor change to your patch, you could kexec the in kexec
> second kernel with x2apic support.
>
My patch can easily avoid the issue by checking max_physical_apicid > 255
instead of x2apic_preenabled.
--
Gleb.
next prev parent reply other threads:[~2009-06-30 18:53 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-30 6:45 [PATCH v4] enable x2APIC without interrupt remapping under KVM Gleb Natapov
2009-06-30 7:18 ` Yinghai Lu
2009-06-30 7:54 ` Gleb Natapov
2009-06-30 18:43 ` Yinghai Lu
2009-06-30 18:53 ` Gleb Natapov [this message]
2009-06-30 15:58 ` Gleb Natapov
2009-06-30 17:00 ` Eric W. Biederman
2009-06-30 17:14 ` Avi Kivity
2009-06-30 19:24 ` Eric W. Biederman
2009-06-30 19:15 ` Gleb Natapov
2009-06-30 17:15 ` Eric W. Biederman
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