linux-kernel - Re: [RESEND] Atomic switch of MSR_IA32_UMWAIT

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <0146cafa-9713-59a7-00b7-87add0ab0738@redhat.com>
Date:   Thu, 23 Jan 2020 17:16:21 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Tao Xu <tao3.xu@...el.com>, Jingqi Liu <jingqi.liu@...el.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND] Atomic switch of MSR_IA32_UMWAIT_CONTROL

On 23/01/20 16:45, Sean Christopherson wrote:
> cc'ing KVM and LKML this time...
> 
> Why does KVM use the atomic load/store lists to load MSR_IA32_UMWAIT_CONTROL
> on VM-Enter/VM-Exit?  Unless the host kernel is doing UWMAIT, which it
> really shouldn't and AFAICT doesn't, isn't it better to use the shared MSR
> mechanism to load the host value only when returning to userspace, and
> reload the guest value on demand?
> 

To clarify, laziness also on part of the reviewer, aka me.

Paolo