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  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Tue, 26 May 2020 18:13:44 -0700
From:   Sean Christopherson <>
To:     Maxim Levitsky <>
Cc:, Paolo Bonzini <>,
        "H. Peter Anvin" <>, Tao Xu <>,
        Jim Mattson <>,, Joerg Roedel <>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <>,
        Wanpeng Li <>,
        Ingo Molnar <>,
        Thomas Gleixner <>,
        Borislav Petkov <>,
        Vitaly Kuznetsov <>,
        Jingqi Liu <>
Subject: Re: [PATCH 0/2] Fix issue with not starting nesting guests on my

On Sat, May 23, 2020 at 07:14:53PM +0300, Maxim Levitsky wrote:
> On my AMD machine I noticed that I can't start any nested guests,
> because nested KVM (everything from master git branches) complains
> that it can't find msr MSR_IA32_UMWAIT_CONTROL which my system doesn't support
> at all anyway.
> I traced it to the recently added UMWAIT support to qemu and kvm.
> The kvm portion exposed the new MSR in KVM_GET_MSR_INDEX_LIST without
> checking that it the underlying feature is supported in CPUID.
> It happened to work when non nested because as a precation kvm,
> tries to read each MSR on host before adding it to that list,
> and when read gets a #GP it ignores it.
> When running nested, the L1 hypervisor can be set to ignore unknown
> msr read/writes (I need this for some other guests), thus this safety
> check doesn't work anymore.
> V2: * added a patch to setup correctly the X86_FEATURE_WAITPKG kvm capability
>     * dropped the cosmetic fix patch as it is now fixed in kvm/queue
> Best regards,
> 	Maxim Levitsky
> Maxim Levitsky (2):
>   kvm/x86/vmx: enable X86_FEATURE_WAITPKG in KVM capabilities
>   kvm/x86: don't expose MSR_IA32_UMWAIT_CONTROL unconditionally

Standard scoping in the shortlog is "KVM: VMX:" and "KVM: x86:".

>  arch/x86/kvm/vmx/vmx.c | 3 +++
>  arch/x86/kvm/x86.c     | 4 ++++
>  2 files changed, 7 insertions(+)
> -- 
> 2.26.2

Powered by blists - more mailing lists