Subject: Re: [PATCH 0/3] Infinite loops in microcode while running guests
To: Paolo Bonzini <pbonzini@redhat.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
References: <1447158174-10484-1-git-send-email-pbonzini@redhat.com>
Cc: digitaleric@google.com
From: Jan Kiszka <jan.kiszka@siemens.com>
Message-ID: <56420F59.7080506@siemens.com>
Date: Tue, 10 Nov 2015 16:38:01 +0100
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On 2015-11-10 13:22, Paolo Bonzini wrote:
> Yes, these can happen.  The issue is that benign exceptions are
> delivered serially, but two of them (#DB and #AC) can also happen
> during exception delivery itself.  The subsequent infinite stream
> of exceptions causes the processor to never exit guest mode.
> 
> Paolo
> 
> Eric Northup (1):
>   KVM: x86: work around infinite loop in microcode when #AC is delivered
> 
> Paolo Bonzini (2):
>   KVM: svm: unconditionally intercept #DB
>   KVM: x86: rename update_db_bp_intercept to update_bp_intercept
> 
>  arch/x86/include/asm/kvm_host.h |  2 +-
>  arch/x86/include/uapi/asm/svm.h |  1 +
>  arch/x86/kvm/svm.c              | 22 +++++++++++-----------
>  arch/x86/kvm/vmx.c              |  7 +++++--
>  arch/x86/kvm/x86.c              |  2 +-
>  5 files changed, 19 insertions(+), 15 deletions(-)
> 

So this affects both Intel and AMD CPUs equally? Nice cross-vendor
"compatibility".

And it can only be triggered via #AC and #DB, or also other exceptions
(that KVM already happens to intercept)? You may guess why I'm asking...

Is any of the issues already documented in a vendor errata?

Thanks,
Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux
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