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Fri, 06 Mar 2020 23:57:31 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 026Nuu0Z193078; Fri, 6 Mar 2020 23:57:31 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3020.oracle.com with ESMTP id 2yg1peh3b0-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 06 Mar 2020 23:57:30 +0000 Received: from abhmp0003.oracle.com (abhmp0003.oracle.com [141.146.116.9]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 026NvQnT003561; Fri, 6 Mar 2020 23:57:26 GMT Received: from localhost.localdomain (/10.159.228.115) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 06 Mar 2020 15:57:26 -0800 Subject: Re: [PATCH v3 2/2] KVM: VMX: untangle VMXON revision_id setting when using eVMCS To: Sean Christopherson Cc: Vitaly Kuznetsov , Paolo Bonzini , Jim Mattson , Wanpeng Li , kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200306130215.150686-1-vkuznets@redhat.com> <20200306130215.150686-3-vkuznets@redhat.com> <908345f1-9bfd-004f-3ba6-0d6dce67d11e@oracle.com> <20200306230747.GA27868@linux.intel.com> From: Krish Sadhukhan Message-ID: Date: Fri, 6 Mar 2020 15:57:25 -0800 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: <20200306230747.GA27868@linux.intel.com> 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=9552 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 malwarescore=0 mlxlogscore=999 mlxscore=0 spamscore=0 adultscore=0 bulkscore=0 suspectscore=2 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003060140 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9552 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 phishscore=0 spamscore=0 impostorscore=0 mlxscore=0 adultscore=0 mlxlogscore=999 lowpriorityscore=0 priorityscore=1501 bulkscore=0 clxscore=1015 suspectscore=2 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003060139 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/6/20 3:07 PM, Sean Christopherson wrote: > On Fri, Mar 06, 2020 at 02:20:13PM -0800, Krish Sadhukhan wrote: >>> @@ -2599,7 +2607,7 @@ void free_loaded_vmcs(struct loaded_vmcs *loaded_vmcs) >>> int alloc_loaded_vmcs(struct loaded_vmcs *loaded_vmcs) >>> { >>> - loaded_vmcs->vmcs = alloc_vmcs(false); >>> + loaded_vmcs->vmcs = alloc_vmcs(VMCS_REGION); >>> if (!loaded_vmcs->vmcs) >>> return -ENOMEM; >>> @@ -2652,25 +2660,13 @@ static __init int alloc_vmxon_regions(void) >>> for_each_possible_cpu(cpu) { >>> struct vmcs *vmcs; >>> - vmcs = alloc_vmcs_cpu(false, cpu, GFP_KERNEL); >>> + /* The VMXON region is really just a special type of VMCS. */ >> >> Not sure if this is the right way to correlate the two. >> >> AFAIU, the SDM calls VMXON region as a memory area that holds the VMCS data >> structure and it calls VMCS the data structure that is used by software to >> switch between VMX root-mode and not-root-mode. So VMXON is a memory area >> whereas VMCS is the structure of the data that resides in that memory area. >> >> So if we follow this interpretation, your enum should rather look like, >> >> enum vmcs_type { >> +    VMCS, >> +    EVMCS, >> +    SHADOW_VMCS > No (to the EVMCS suggestion), because this allocation needs to happen for > !eVMCS. The SDM never explictly calls the VMXON region a VMCS, but it's > just being coy. E.g. VMCLEAR doesn't fail if you point it at random > memory, but point it at the VMXON region and it yells. > > We could call it VMXON_VMCS if that helps. Are you saying, + enum vmcs_type { +     VMXON_REGION, +     VMXON_VMCS, +     SHADOW_VMCS_REGION, +}; ? In that case, "VMXON_REGION" and "VMXON_VMCS" are no different according to your explanation. > The SDM does call the memory > allocation for regular VMCSes a "VMCS region": > > A logical processor associates a region in memory with each VMCS. This > region is called the VMCS region. > > I don't think I've ever heard anyone differentiate that two though, i.e. > VMCS is used colloquially to mean both the data structure itself and the > memory region containing the data structure. > >>> + vmcs = alloc_vmcs_cpu(VMXON_REGION, cpu, GFP_KERNEL); >>> if (!vmcs) { >>> free_vmxon_regions(); >>> return -ENOMEM; >>> } >>> - /* >>> - * When eVMCS is enabled, alloc_vmcs_cpu() sets >>> - * vmcs->revision_id to KVM_EVMCS_VERSION instead of >>> - * revision_id reported by MSR_IA32_VMX_BASIC. >>> - * >>> - * However, even though not explicitly documented by >>> - * TLFS, VMXArea passed as VMXON argument should >>> - * still be marked with revision_id reported by >>> - * physical CPU. >>> - */ >>> - if (static_branch_unlikely(&enable_evmcs)) >>> - vmcs->hdr.revision_id = vmcs_config.revision_id; >>> - >>> per_cpu(vmxarea, cpu) = vmcs; >>> } >>> return 0; >>> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h >>> index e64da06c7009..a5eb92638ac2 100644 >>> --- a/arch/x86/kvm/vmx/vmx.h >>> +++ b/arch/x86/kvm/vmx/vmx.h >>> @@ -489,16 +489,22 @@ static inline struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu *vcpu) >>> return &(to_vmx(vcpu)->pi_desc); >>> } >>> -struct vmcs *alloc_vmcs_cpu(bool shadow, int cpu, gfp_t flags); >>> +enum vmcs_type { >>> + VMXON_REGION, >>> + VMCS_REGION, >>> + SHADOW_VMCS_REGION, >>> +}; >>> + >>> +struct vmcs *alloc_vmcs_cpu(enum vmcs_type type, int cpu, gfp_t flags); >>> void free_vmcs(struct vmcs *vmcs); >>> int alloc_loaded_vmcs(struct loaded_vmcs *loaded_vmcs); >>> void free_loaded_vmcs(struct loaded_vmcs *loaded_vmcs); >>> void loaded_vmcs_init(struct loaded_vmcs *loaded_vmcs); >>> void loaded_vmcs_clear(struct loaded_vmcs *loaded_vmcs); >>> -static inline struct vmcs *alloc_vmcs(bool shadow) >>> +static inline struct vmcs *alloc_vmcs(enum vmcs_type type) >>> { >>> - return alloc_vmcs_cpu(shadow, raw_smp_processor_id(), >>> + return alloc_vmcs_cpu(type, raw_smp_processor_id(), >>> GFP_KERNEL_ACCOUNT); >>> }