linux-kernel - Re: [PATCH v11 10/13] KVM: x86: Introduce new KVM_FEATURE_SEV_LIVE

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20210406135950.GA23358@ashkalra_ubuntu_server>
Date:   Tue, 6 Apr 2021 13:59:50 +0000
From:   Ashish Kalra <ashish.kalra@....com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Steve Rutherford <srutherford@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Joerg Roedel <joro@...tes.org>,
        Borislav Petkov <bp@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        X86 ML <x86@...nel.org>, KVM list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Venu Busireddy <venu.busireddy@...cle.com>,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v11 10/13] KVM: x86: Introduce new
 KVM_FEATURE_SEV_LIVE_MIGRATION feature & Custom MSR.

Hello Paolo,

On Tue, Apr 06, 2021 at 03:47:59PM +0200, Paolo Bonzini wrote:
> On 06/04/21 15:26, Ashish Kalra wrote:
> > > It's a little unintuitive to see KVM_MSR_RET_FILTERED here, since
> > > userspace can make this happen on its own without having an entry in
> > > this switch statement (by setting it in the msr filter bitmaps). When
> > > using MSR filters, I would only expect to get MSR filter exits for
> > > MSRs I specifically asked for.
> > > 
> > > Not a huge deal, just a little unintuitive. I'm not sure other options
> > > are much better (you could put KVM_MSR_RET_INVALID, or you could just
> > > not have these entries in svm_{get,set}_msr).
> > > 
> > Actually KVM_MSR_RET_FILTERED seems more logical to use, especially in
> > comparison with KVM_MSR_RET_INVALID.
> > 
> > Also, hooking this msr in svm_{get,set}_msr allows some in-kernel error
> > pre-processsing before doing the pass-through to userspace.
> 
> I agree that it should be up to userspace to set up the filter since we now
> have that functionality.
> 

The userspace is still setting up the filter and handling this MSR, it
is only some basic error pre-processing being done in-kernel here.

Thanks,
Ashish

> Let me read the whole threads for the past versions to see what the
> objections were...
> 
> Paolo
>