linux-kernel - Re: [RESEND PATCH v4 04/10] KVM: vmx/pmu: Add MSR_ARCH_LBR

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

Message-ID: <CALMp9eQG+JLnHe4zRKg0sHtxynSiGGKPw--5J+cY2-f3QWRW2A@mail.gmail.com>
Date:   Wed, 23 Jun 2021 11:29:08 -0700
From:   Jim Mattson <jmattson@...gle.com>
To:     Like Xu <like.xu@...ux.intel.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>,
        Yang Weijiang <weijiang.yang@...el.com>,
        Wei Wang <wei.w.wang@...el.com>,
        kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND PATCH v4 04/10] KVM: vmx/pmu: Add MSR_ARCH_LBR_CTL
 emulation for Arch LBR

On Mon, May 10, 2021 at 1:16 AM Like Xu <like.xu@...ux.intel.com> wrote:
>
> Arch LBRs are enabled by setting MSR_ARCH_LBR_CTL.LBREn to 1. A new guest
> state field named "Guest IA32_LBR_CTL" is added to enhance guest LBR usage.
> When guest Arch LBR is enabled, a guest LBR event will be created like the
> model-specific LBR does.
>
> On processors that support Arch LBR, MSR_IA32_DEBUGCTLMSR[bit 0] has no
> meaning. It can be written to 0 or 1, but reads will always return 0.
> Like IA32_DEBUGCTL, IA32_ARCH_LBR_CTL msr is also reserved on INIT.
>
> Signed-off-by: Like Xu <like.xu@...ux.intel.com>
> ---
>  arch/x86/events/intel/lbr.c      |  2 --
>  arch/x86/include/asm/msr-index.h |  1 +
>  arch/x86/include/asm/vmx.h       |  2 ++
>  arch/x86/kvm/vmx/pmu_intel.c     | 31 ++++++++++++++++++++++++++-----
>  arch/x86/kvm/vmx/vmx.c           |  9 +++++++++
>  5 files changed, 38 insertions(+), 7 deletions(-)
>
Same comments as on the previous patch. Your guard for ensuring that
the new VMCS fields exist can be spoofed by a malicious userspace, and
the new MSR has to be enumerated by KVM_GET_MSR_INDEX_LIST.