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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id m9sm14716090wrs.36.2021.05.24.05.00.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 May 2021 05:00:38 -0700 (PDT) From: Vitaly Kuznetsov To: Eduardo Habkost Subject: Re: [PATCH v6 10/19] i386: move eVMCS enablement to hyperv_init_vcpu() In-Reply-To: <20210521212021.lsf2pzfu647ocqj3@habkost.net> References: <20210422161130.652779-1-vkuznets@redhat.com> <20210422161130.652779-11-vkuznets@redhat.com> <20210521212021.lsf2pzfu647ocqj3@habkost.net> Date: Mon, 24 May 2021 14:00:37 +0200 Message-ID: <87mtsk734q.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=vkuznets@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=216.205.24.124; envelope-from=vkuznets@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -31 X-Spam_score: -3.2 X-Spam_bar: --- X-Spam_report: (-3.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.371, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , Marcelo Tosatti , qemu-devel@nongnu.org, Igor Mammedov Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Eduardo Habkost writes: > On Thu, Apr 22, 2021 at 06:11:21PM +0200, Vitaly Kuznetsov wrote: >> hyperv_expand_features() will be called before we create vCPU so >> evmcs enablement should go away. hyperv_init_vcpu() looks like the >> right place. >> >> Signed-off-by: Vitaly Kuznetsov >> --- >> target/i386/kvm/kvm.c | 60 ++++++++++++++++++++++++++----------------- >> 1 file changed, 37 insertions(+), 23 deletions(-) >> >> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c >> index 6b391db7a030..a2ef2dc154a2 100644 >> --- a/target/i386/kvm/kvm.c >> +++ b/target/i386/kvm/kvm.c >> @@ -962,6 +962,7 @@ static struct kvm_cpuid2 *get_supported_hv_cpuid(CPUState *cs) >> { >> struct kvm_cpuid2 *cpuid; >> int max = 7; /* 0x40000000..0x40000005, 0x4000000A */ >> + int i; >> >> /* >> * When the buffer is too small, KVM_GET_SUPPORTED_HV_CPUID fails with >> @@ -971,6 +972,22 @@ static struct kvm_cpuid2 *get_supported_hv_cpuid(CPUState *cs) >> while ((cpuid = try_get_hv_cpuid(cs, max)) == NULL) { >> max++; >> } >> + >> + /* >> + * KVM_GET_SUPPORTED_HV_CPUID does not set EVMCS CPUID bit before >> + * KVM_CAP_HYPERV_ENLIGHTENED_VMCS is enabled but we want to get the >> + * information early, just check for the capability and set the bit >> + * manually. >> + */ > > Should we add a comment noting that this hack won't be necessary > if using the system ioctl? I assume we still want to support > Linux < v5.11 for a while, so simply Not exactly sure what was supposed to be here but yes, the hack is not needed with system KVM_GET_SUPPORTED_HV_CPUID ioctl but we want to support older kernels. > > >> + if (kvm_check_extension(cs->kvm_state, >> + KVM_CAP_HYPERV_ENLIGHTENED_VMCS) > 0) { >> + for (i = 0; i < cpuid->nent; i++) { >> + if (cpuid->entries[i].function == HV_CPUID_ENLIGHTMENT_INFO) { >> + cpuid->entries[i].eax |= HV_ENLIGHTENED_VMCS_RECOMMENDED; >> + } >> + } >> + } >> + >> return cpuid; >> } >> >> @@ -1200,24 +1217,6 @@ static int hyperv_expand_features(CPUState *cs) >> if (!hyperv_enabled(cpu)) >> return 0; >> >> - if (hyperv_feat_enabled(cpu, HYPERV_FEAT_EVMCS) || >> - cpu->hyperv_passthrough) { >> - uint16_t evmcs_version; >> - >> - r = kvm_vcpu_enable_cap(cs, KVM_CAP_HYPERV_ENLIGHTENED_VMCS, 0, >> - (uintptr_t)&evmcs_version); >> - >> - if (hyperv_feat_enabled(cpu, HYPERV_FEAT_EVMCS) && r) { >> - fprintf(stderr, "Hyper-V %s is not supported by kernel\n", >> - kvm_hyperv_properties[HYPERV_FEAT_EVMCS].desc); >> - return -ENOSYS; >> - } >> - >> - if (!r) { >> - cpu->hyperv_nested[0] = evmcs_version; >> - } >> - } >> - >> if (cpu->hyperv_passthrough) { >> cpu->hyperv_vendor_id[0] = >> hv_cpuid_get_host(cs, HV_CPUID_VENDOR_AND_MAX_FUNCTIONS, R_EBX); >> @@ -1455,6 +1454,21 @@ static int hyperv_init_vcpu(X86CPU *cpu) >> } >> } >> >> + if (hyperv_feat_enabled(cpu, HYPERV_FEAT_EVMCS)) { >> + uint16_t evmcs_version; >> + >> + ret = kvm_vcpu_enable_cap(cs, KVM_CAP_HYPERV_ENLIGHTENED_VMCS, 0, >> + (uintptr_t)&evmcs_version); >> + >> + if (ret < 0) { >> + fprintf(stderr, "Hyper-V %s is not supported by kernel\n", >> + kvm_hyperv_properties[HYPERV_FEAT_EVMCS].desc); >> + return ret; >> + } >> + >> + cpu->hyperv_nested[0] = evmcs_version; > > Wait, won't this break guest ABI? Do we want to make > HYPERV_FEAT_EVMCS a migration blocker until this is fixed? > Could you please elaborate on the issue? I read the above is: when evmcs' feature was requested, make an attempt to enable KVM_CAP_HYPERV_ENLIGHTENED_VMCS, and bail out if this fails. Propagate the the acquired evmcs version to 'cpu->hyperv_nested[]' otherwise. > >> + } >> + >> return 0; >> } >> >> @@ -1519,6 +1533,11 @@ int kvm_arch_init_vcpu(CPUState *cs) >> } >> >> if (hyperv_enabled(cpu)) { >> + r = hyperv_init_vcpu(cpu); >> + if (r) { >> + return r; >> + } >> + >> cpuid_i = hyperv_fill_cpuids(cs, cpuid_data.entries); >> kvm_base = KVM_CPUID_SIGNATURE_NEXT; >> has_msr_hv_hypercall = true; >> @@ -1868,11 +1887,6 @@ int kvm_arch_init_vcpu(CPUState *cs) >> >> kvm_init_msrs(cpu); >> >> - r = hyperv_init_vcpu(cpu); >> - if (r) { >> - goto fail; >> - } >> - >> return 0; > > I would move the two hunks above to a separate patch, but not a > big deal. The guest ABI issue is existing, and the comment > suggestion can be done in a follow up patch, so: > > Reviewed-by: Eduardo Habkost > Thanks! >> >> fail: >> -- >> 2.30.2 >> -- Vitaly