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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id h14sm7360763wmb.1.2021.05.24.05.08.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 May 2021 05:08:27 -0700 (PDT) From: Vitaly Kuznetsov To: Eduardo Habkost Subject: Re: [PATCH v6 13/19] i386: prefer system KVM_GET_SUPPORTED_HV_CPUID ioctl over vCPU's one In-Reply-To: <20210521214202.g222ullptiseaesq@habkost.net> References: <20210422161130.652779-1-vkuznets@redhat.com> <20210422161130.652779-14-vkuznets@redhat.com> <20210521214202.g222ullptiseaesq@habkost.net> Date: Mon, 24 May 2021 14:08:26 +0200 Message-ID: <87h7is72rp.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=170.10.133.124; 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 06:11:24PM +0200, Vitaly Kuznetsov wrote: >> KVM_GET_SUPPORTED_HV_CPUID was made a system wide ioctl which can be called >> prior to creating vCPUs and we are going to use that to expand Hyper-V cpu >> features early. Use it when it is supported by KVM. >> >> Signed-off-by: Vitaly Kuznetsov >> --- >> target/i386/kvm/kvm.c | 17 +++++++++++++---- >> 1 file changed, 13 insertions(+), 4 deletions(-) >> >> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c >> index feec9f25ba12..5d08f3a39ef7 100644 >> --- a/target/i386/kvm/kvm.c >> +++ b/target/i386/kvm/kvm.c >> @@ -928,7 +928,8 @@ static struct { >> }, >> }; >> >> -static struct kvm_cpuid2 *try_get_hv_cpuid(CPUState *cs, int max) >> +static struct kvm_cpuid2 *try_get_hv_cpuid(CPUState *cs, int max, >> + bool do_sys_ioctl) >> { >> struct kvm_cpuid2 *cpuid; >> int r, size; >> @@ -937,7 +938,11 @@ static struct kvm_cpuid2 *try_get_hv_cpuid(CPUState *cs, int max) >> cpuid = g_malloc0(size); >> cpuid->nent = max; >> >> - r = kvm_vcpu_ioctl(cs, KVM_GET_SUPPORTED_HV_CPUID, cpuid); >> + if (do_sys_ioctl) { >> + r = kvm_ioctl(kvm_state, KVM_GET_SUPPORTED_HV_CPUID, cpuid); >> + } else { >> + r = kvm_vcpu_ioctl(cs, KVM_GET_SUPPORTED_HV_CPUID, cpuid); >> + } >> if (r == 0 && cpuid->nent >= max) { >> r = -E2BIG; >> } >> @@ -964,13 +969,17 @@ static struct kvm_cpuid2 *get_supported_hv_cpuid(CPUState *cs) >> /* 0x40000000..0x40000005, 0x4000000A, 0x40000080..0x40000080 leaves */ >> int max = 10; >> int i; >> + bool do_sys_ioctl; >> + >> + do_sys_ioctl = >> + kvm_check_extension(kvm_state, KVM_CAP_SYS_HYPERV_CPUID) > 0; >> >> /* >> * When the buffer is too small, KVM_GET_SUPPORTED_HV_CPUID fails with >> * -E2BIG, however, it doesn't report back the right size. Keep increasing >> * it and re-trying until we succeed. >> */ >> - while ((cpuid = try_get_hv_cpuid(cs, max)) == NULL) { >> + while ((cpuid = try_get_hv_cpuid(cs, max, do_sys_ioctl)) == NULL) { >> max++; >> } >> >> @@ -980,7 +989,7 @@ static struct kvm_cpuid2 *get_supported_hv_cpuid(CPUState *cs) >> * information early, just check for the capability and set the bit >> * manually. >> */ >> - if (kvm_check_extension(cs->kvm_state, >> + if (!do_sys_ioctl && kvm_check_extension(cs->kvm_state, >> KVM_CAP_HYPERV_ENLIGHTENED_VMCS) > 0) { > > Oh, this conditional replaces the comment I suggested in patch > 10/19. It makes it obvious that the hack can be deleted if we > remove support for the VCPU ioctl. > > So, when exactly will we be able to delete the VCPU ioctl code > and support only the system ioctl? When QEMU drops support for kernels < 5.11? Note, current RHEL8 already supports system version so we're talking about upstream kernels/Ubuntu LTS/... I remember there was a list of supported kernels for QEMU somewhere but don't seem to be able to find it quickly, could you maybe point me in the right direction? > > Reviewed-by: Eduardo Habkost > Thanks! >> for (i = 0; i < cpuid->nent; i++) { >> if (cpuid->entries[i].function == HV_CPUID_ENLIGHTMENT_INFO) { >> -- >> 2.30.2 >> -- Vitaly