linux-kernel - Re: [RFC PATCH 1/3] kvm: x86: Rename KVM_DEBUGREG_RELOAD to KVM_DEBUGREG_NEED

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]

Date:   Sat, 25 Apr 2020 09:54:07 -0700
From:   Nadav Amit <nadav.amit@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Xiaoyao Li <xiaoyao.li@...el.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        kvm <kvm@...r.kernel.org>, Nadav Amit <namit@...technion.ac.il>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/3] kvm: x86: Rename KVM_DEBUGREG_RELOAD to
 KVM_DEBUGREG_NEED_RELOAD

> On Apr 25, 2020, at 1:07 AM, Paolo Bonzini <pbonzini@...hat.com> wrote:
> 
> On 16/04/20 12:15, Xiaoyao Li wrote:
>> To make it more clear that the flag means DRn (except DR7) need to be
>> reloaded before vm entry.
>> 
>> Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
> 
> I wonder if KVM_DEBUGREG_RELOAD is needed at all.  It should be easy to
> write selftests for it, using the testcase in commit message
> 172b2386ed16 and the information in commit ae561edeb421.

I must be missing something, since I did not follow this thread and other
KVM changes very closely.

Yet, for the record, I added KVM_DEBUGREG_RELOAD due to real experienced
issues that I had while running Intel’s fuzzing tests on KVM: IIRC, the DRs
were not reloaded after an INIT event that clears them.

Personally, I would prefer that a test for that, if added, would be added
to KVM-unit-tests, based on Liran’s INIT test. This would allow to confirm
bare-metal behaves as the VM.