linux-kernel - Re: [PATCH 0/4] Add support for XMM fast hypercalls

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: <53200f24-bd57-1509-aee2-0723aa8a3f6f@redhat.com>
Date:   Thu, 8 Apr 2021 17:48:19 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Siddharth Chandrasekaran <sidcha@...zon.de>
Cc:     Wei Liu <wei.liu@...nel.org>, kys@...rosoft.com,
        haiyangz@...rosoft.com, sthemmin@...rosoft.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        seanjc@...gle.com, vkuznets@...hat.com, wanpengli@...cent.com,
        jmattson@...gle.com, joro@...tes.org, graf@...zon.com,
        eyakovl@...zon.de, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH 0/4] Add support for XMM fast hypercalls

On 08/04/21 17:40, Siddharth Chandrasekaran wrote:
>>>> Although the Hyper-v TLFS mentions that a guest cannot use this feature
>>>> unless the hypervisor advertises support for it, some hypercalls which
>>>> we plan on upstreaming in future uses them anyway.
>>> No, please don't do this. Check the feature bit(s) before you issue
>>> hypercalls which rely on the extended interface.
>> Perhaps Siddharth should clarify this, but I read it as Hyper-V being
>> buggy and using XMM arguments unconditionally.
> The guest is at fault here as it expects Hyper-V to consume arguments
> from XMM registers for certain hypercalls (that we are working) even if
> we didn't expose the feature via CPUID bits.

What guest is that?

Paolo