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Wed, 21 Aug 2019 23:05:08 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x7LN3BOH039436; Wed, 21 Aug 2019 23:05:08 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by userp3020.oracle.com with ESMTP id 2uh83p8cjd-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 21 Aug 2019 23:05:08 +0000 Received: from abhmp0003.oracle.com (abhmp0003.oracle.com [141.146.116.9]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x7LN56ha018818; Wed, 21 Aug 2019 23:05:06 GMT Received: from [10.159.144.137] (/10.159.144.137) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 21 Aug 2019 16:05:05 -0700 Subject: Re: [PATCH 6/8][KVM nVMX]: Load IA32_PERF_GLOBAL_CTRL MSR on vmentry of nested guests To: Jim Mattson Cc: kvm list , Paolo Bonzini , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= References: <20190424231724.2014-1-krish.sadhukhan@oracle.com> <20190424231724.2014-7-krish.sadhukhan@oracle.com> From: Krish Sadhukhan Message-ID: <6d0a81be-1546-2a02-92b3-6b94468de9c6@oracle.com> Date: Wed, 21 Aug 2019 16:05:04 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9355 signatures=668684 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908210228 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9355 signatures=668684 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908210228 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 8/15/19 3:44 PM, Jim Mattson wrote: > On Wed, Apr 24, 2019 at 4:43 PM Krish Sadhukhan > wrote: >> According to section "Loading Guest State" in Intel SDM vol 3C, the >> IA32_PERF_GLOBAL_CTRL MSR is loaded on vmentry of nested guests: >> >> "If the “load IA32_PERF_GLOBAL_CTRL” VM-entry control is 1, the >> IA32_PERF_GLOBAL_CTRL MSR is loaded from the IA32_PERF_GLOBAL_CTRL >> field." >> >> Signed-off-by: Krish Sadhukhan >> Suggested-by: Jim Mattson >> Reviewed-by: Karl Heubaum >> --- >> arch/x86/kvm/vmx/nested.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c >> index a7bf19eaa70b..8177374886a9 100644 >> --- a/arch/x86/kvm/vmx/nested.c >> +++ b/arch/x86/kvm/vmx/nested.c >> @@ -2300,6 +2300,10 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12, >> vcpu->arch.cr0_guest_owned_bits &= ~vmcs12->cr0_guest_host_mask; >> vmcs_writel(CR0_GUEST_HOST_MASK, ~vcpu->arch.cr0_guest_owned_bits); >> >> + if (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL) >> + vmcs_write64(GUEST_IA32_PERF_GLOBAL_CTRL, >> + vmcs12->guest_ia32_perf_global_ctrl); >> + >> if (vmx->nested.nested_run_pending && >> (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_PAT)) { >> vmcs_write64(GUEST_IA32_PAT, vmcs12->guest_ia32_pat); >> -- >> 2.17.2 >> > This isn't quite right. The GUEST_IA32_PERF_GLOBAL_CTRL value is just > going to get overwritten later by atomic_switch_perf_msrs(). atomic_switch_perf_msrs() gest called from vmx_vcpu_run() which I thought was executing before handle_vmlaunch() stuff that lead to prepare_vmcs02(). Did I miss something in the call-chain ? > Instead of writing the vmcs12 value directly into the vmcs02, you > should call kvm_set_msr(), exactly as it would have been called if > MSR_CORE_PERF_GLOBAL_CTRL had been in the vmcs12 > VM-entry MSR-load list. Then, atomic_switch_perf_msrs() will > automatically do the right thing.