From: Andi Kleen <ak@linux.intel.com>
To: Wei Wang <wei.w.wang@intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"Liang, Kan" <kan.liang@intel.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"mingo@redhat.com" <mingo@redhat.com>,
"rkrcmar@redhat.com" <rkrcmar@redhat.com>,
"Xu, Like" <like.xu@intel.com>
Subject: Re: [PATCH v2 6/8] perf/x86/intel/lbr: guest requesting KVM for lbr stack save/restore
Date: Fri, 7 Sep 2018 07:10:51 -0700 [thread overview]
Message-ID: <20180907141051.GP27886@tassilo.jf.intel.com> (raw)
In-Reply-To: <5B920B96.6080803@intel.com>
> This could achieve the above #1, but how would it solve #2 above? That is,
> after the guest uses the lbr feature for a while, the lbr stack has been
> passed through, then the guest doesn't use lbr any more, but the vCPU will
> still save/restore on switching?
If nothing accesses the MSR LBRs after a context switch in the guest
nothing gets saved/restored due to:
> > Also when the LBRs haven't been set to direct access the state doesn't
> > need to be saved.
-Andi
next prev parent reply other threads:[~2018-09-07 14:10 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-06 11:30 [PATCH v2 0/8] Guest LBR Enabling Wei Wang
2018-09-06 11:30 ` [PATCH v2 1/8] perf/x86: add a function to get the lbr stack Wei Wang
2018-09-07 3:28 ` Andi Kleen
2018-09-07 6:45 ` Wei Wang
2018-09-06 11:30 ` [PATCH v2 2/8] KVM/x86: KVM_CAP_X86_GUEST_LBR Wei Wang
2018-09-06 11:30 ` [PATCH v2 3/8] KVM/vmx: Pass through the lbr stack to a guest Wei Wang
2018-09-06 11:30 ` [PATCH v2 4/8] KVM/x86: expose MSR_IA32_PERF_CAPABILITIES to the guest Wei Wang
2018-09-06 11:30 ` [PATCH v2 5/8] KVM/x86: enable the guest to access the debugctl msr Wei Wang
2018-09-06 11:30 ` [PATCH v2 6/8] perf/x86/intel/lbr: guest requesting KVM for lbr stack save/restore Wei Wang
2018-09-07 3:27 ` Andi Kleen
2018-09-07 5:24 ` Wei Wang
2018-09-07 14:10 ` Andi Kleen [this message]
2018-09-07 15:20 ` Wang, Wei W
2018-09-07 20:05 ` Andi Kleen
2018-09-08 1:34 ` Wang, Wei W
2018-09-06 11:30 ` [PATCH v2 7/8] KVM: PMU: support to save/restore the guest lbr stack on vCPU switching Wei Wang
2018-09-07 14:36 ` Jann Horn
2018-09-07 15:21 ` Wang, Wei W
2018-09-18 0:58 ` Gonglei (Arei)
2018-09-18 2:56 ` Andi Kleen
2018-09-18 9:57 ` Wei Wang
2018-09-18 10:34 ` Gonglei (Arei)
2018-09-06 11:30 ` [PATCH v2 8/8] perf/x86/intel/lbr: add the guest_lbr boolean to cpuc Wei Wang
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