linux-kernel - Re: [PATCH v10 0/2] x86: vmclear vmcss on all cpus when doing kdump if necessary

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Date:	Wed, 05 Dec 2012 11:35:58 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Zhang Yanfei <zhangyanfei@...fujitsu.com>
Cc:	Marcelo Tosatti <mtosatti@...hat.com>,
	Gleb Natapov <gleb@...hat.com>,
	"kexec\@lists.infradead.org" <kexec@...ts.infradead.org>,
	"kvm\@vger.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 0/2] x86: vmclear vmcss on all cpus when doing kdump if necessary

Zhang Yanfei <zhangyanfei@...fujitsu.com> writes:

> Currently, kdump just makes all the logical processors leave VMX operation by
> executing VMXOFF instruction, so any VMCSs active on the logical processors may
> be corrupted. But, sometimes, we need the VMCSs to debug guest images contained
> in the host vmcore. To prevent the corruption, we should VMCLEAR the VMCSs before
> executing the VMXOFF instruction.
>
> The patch set provides a way to VMCLEAR vmcss related to guests on all cpus before
> executing the VMXOFF when doing kdump. This is used to ensure the VMCSs in the
> vmcore updated and non-corrupted.

Skimming through it looks like the important things have been addressed.

Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>


> Changelog from v9 to v10:
> 1. add rcu protect to the callback function
>
> Changelog from v8 to v9:
> 1. KEXEC: use a callback function instead of a notifier.
> 2. KVM-INTEL: use a new vmclear function instead of just calling 
>    vmclear_local_loaded_vmcss to make sure we just do the core vmclear
>    operation in kdump.
>
> Changelog from v7 to v8:
> 1. KEXEC: regression for using name crash_notifier_list
>    and remove comments related to KVM
>    and just call function atomic_notifier_call_chain directly.
>
> Changelog from v6 to v7:
> 1. KVM-INTEL: in hardware_disable, we needn't disable the
>    vmclear, so remove it.
>
> Changelog from v5 to v6:
> 1. KEXEC: the atomic notifier list renamed:
>    crash_notifier_list --> vmclear_notifier_list
> 2. KVM-INTEL: provide empty functions if CONFIG_KEXEC is
>    not defined and remove unnecessary #ifdef's.
>
> Changelog from v4 to v5:
> 1. use an atomic notifier instead of function call, so
>    have all the vmclear codes in vmx.c.
>
> Changelog from v3 to v4:
> 1. add a new percpu variable vmclear_skipped to skip
>    vmclear in kdump in some conditions.
>
> Changelog from v2 to v3:
> 1. remove unnecessary conditions in function
>    cpu_emergency_clear_loaded_vmcss as Marcelo suggested.
>
> Changelog from v1 to v2:
> 1. remove the sysctl and clear VMCSs unconditionally.
>
> Zhang Yanfei (2):
>   x86/kexec: VMCLEAR VMCSs loaded on all cpus if necessary
>   KVM-INTEL: provide the vmclear function and a bitmap to support
>     VMCLEAR in kdump
>
>  arch/x86/include/asm/kexec.h |    2 +
>  arch/x86/kernel/crash.c      |   32 ++++++++++++++++++++
>  arch/x86/kvm/vmx.c           |   67 ++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 101 insertions(+), 0 deletions(-)
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