linux-kernel - Re: [PATCH v4 0/2] x86: clear vmcss on all cpus when doing kdump if necessary

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Date:	Mon, 19 Nov 2012 22:32:58 -0200
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	zhangyanfei <zhangyanfei@...fujitsu.com>
Cc:	"x86@...nel.org" <x86@...nel.org>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	Avi Kivity <avi@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH v4 0/2] x86: clear vmcss on all cpus when doing kdump if
 necessary

On Fri, Nov 16, 2012 at 06:12:58PM +0800, zhangyanfei wrote:
> Hello Marcelo,
> 
> Any thoughts?

I thought a function call was OK, but its better to have all code in
vmx.c. Please have an atomic notifier in kexec.c (registered by KVM
module via atomic_notifier_chain_register etc).

Other than that, which is largely cosmetic, it looks fine.
Sorry for not expressing this earlier.


> 于 2012年11月14日 17:29, zhangyanfei 写道:
> > 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.
> > 
> > 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 on all cpus if necessary
> >   KVM: set/unset crash_clear_loaded_vmcss and vmclear_skipped in
> >     kvm_intel module
> > 
> >  arch/x86/include/asm/kexec.h |    3 +++ 
> >  arch/x86/kernel/crash.c      |   32 ++++++++++++++++++++++++++++++++
> >  arch/x86/kvm/vmx.c           |   32 ++++++++++++++++++++++++++++++++
> >  3 files changed, 67 insertions(+), 0 deletions(-)
> > 
> > 
> > --
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> 
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