linux-kernel - Re: [PATCH v11 7/9] KVM: X86: Add userspace access interface for CET MSRs

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Date:   Tue, 28 Apr 2020 21:41:07 +0800
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Yang Weijiang <weijiang.yang@...el.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, sean.j.christopherson@...el.com,
        jmattson@...gle.com, yu.c.zhang@...ux.intel.com
Subject: Re: [PATCH v11 7/9] KVM: X86: Add userspace access interface for CET
 MSRs

On Mon, Apr 27, 2020 at 04:04:28PM +0200, Paolo Bonzini wrote:
> On 26/04/20 17:23, Yang Weijiang wrote:
> > What's the purpose of the selftest? Is it just for Shadow Stack SSP
> > state transitions in various cases? e.g., L0 SSP<--->L3 SSP,
> > L0 SSP1<--->L0 SSP2?
> 
> No, it checks that the whole state can be extracted and restored from a
> running VM.  For example, it would have caught immediately that the
> current SSP could not be saved and restored.
> 
> > We now have the KVM unit-test for CET functionalities,
> > i.e., Shadow Stack and Indirect Branch Tracking for user-mode, I can put the
> > state test app into the todo list as current patchset is mainly for user-mode
> > protection, the supervisor-mode CET protection is the next step.
> 
> What are the limitations?  Or are you referring to the unit test?
>
I'm referring to the unit test, I enabled basic CET function test to verify
if SHSTK/IBT is supported with current platform and KVM, but didn't cover
what you mentioned above. OK, I put the state
self-test to my todo list. Thank you for the reminder.

> Paolo