From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joerg Roedel <joro@8bytes.org>
Subject: Re: [PATCH] Use WARN_ON_ONCE for missing X86_FEATURE_NRIPS
Date: Wed, 7 Oct 2015 13:03:36 +0200
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Cc: Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org,
	Dirk =?iso-8859-1?Q?M=FCller?= <dmueller@suse.com>
To: Bandan Das <bsd@redhat.com>
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On Tue, Oct 06, 2015 at 01:59:27PM -0400, Bandan Das wrote:
> Joerg Roedel <joro@8bytes.org> writes:
> >
> > So svm->vmcb->control.next_rip is only written by hardware or in
> > svm_check_intercept(). Both cases write only to this field, if the
> > hardware supports X86_FEATURE_NRIPS. The write in nested_svm_vmexit only
> 
> Not until commit f104765b4f81fd74d69e0eb161e89096deade2db. So, an older L1
> kernel will trigger it.

But we don't care if L1 writes something into its own next_rip, as we
never read this value from its VMCB. We only copy the next_rip value we
get from our shadow-vmcb to it on an emulated vmexit. So I still don't
understand what triggers the reported problem or why the WARN_ON is
necessary.


	Joerg