linux-kernel - Re: [RFC PATCH 28/41] KVM: x86/pmu: Switch IA32_PERF_GLOBAL

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: <CALMp9eTQr8ndf48uHHDem2ZkycdhAuVqz18+V1reEEfv0sx8qg@mail.gmail.com>
Date: Thu, 11 Apr 2024 15:10:54 -0700
From: Jim Mattson <jmattson@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Xiong Zhang <xiong.y.zhang@...ux.intel.com>, pbonzini@...hat.com, 
	peterz@...radead.org, mizhang@...gle.com, kan.liang@...el.com, 
	zhenyuw@...ux.intel.com, dapeng1.mi@...ux.intel.com, kvm@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	zhiyuan.lv@...el.com, eranian@...gle.com, irogers@...gle.com, 
	samantha.alt@...el.com, like.xu.linux@...il.com, chao.gao@...el.com, 
	Xiong Zhang <xiong.y.zhang@...el.com>
Subject: Re: [RFC PATCH 28/41] KVM: x86/pmu: Switch IA32_PERF_GLOBAL_CTRL at
 VM boundary

On Thu, Apr 11, 2024 at 2:54 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> On Fri, Jan 26, 2024, Xiong Zhang wrote:
> > +static void save_perf_global_ctrl_in_passthrough_pmu(struct vcpu_vmx *vmx)
> > +{
> > +     struct kvm_pmu *pmu = vcpu_to_pmu(&vmx->vcpu);
> > +     int i;
> > +
> > +     if (vm_exit_controls_get(vmx) & VM_EXIT_SAVE_IA32_PERF_GLOBAL_CTRL) {
> > +             pmu->global_ctrl = vmcs_read64(GUEST_IA32_PERF_GLOBAL_CTRL);
> > +     } else {
> > +             i = vmx_find_loadstore_msr_slot(&vmx->msr_autostore.guest,
> > +                                             MSR_CORE_PERF_GLOBAL_CTRL);
> > +             if (i < 0)
> > +                     return;
> > +             pmu->global_ctrl = vmx->msr_autostore.guest.val[i].value;
>
> As before, NAK to using the MSR load/store lists unless there's a *really* good
> reason I'm missing.

The VM-exit control, "save IA32_PERF_GLOBAL_CTL," first appears in
Sapphire Rapids. I think that's a compelling reason.

> And we should consider adding VCPU_EXREG_GLOBAL_CTRL so that we can defer the
> VMREAD until KVM actually tries to access the guest value.