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X-CSE-ConnectionGUID: n2lCndQhT5umCUGaNPJIjQ== X-CSE-MsgGUID: j+5m7M7DRxWEFPk+yNE40g== X-IronPort-AV: E=McAfee;i="6700,10204,11314"; a="47640483" X-IronPort-AV: E=Sophos;i="6.12,314,1728975600"; d="scan'208";a="47640483" Received: from orviesa006.jf.intel.com ([10.64.159.146]) by orvoesa103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jan 2025 04:39:46 -0800 X-CSE-ConnectionGUID: 8RJqrxEAS0ClqBKgQtivpA== X-CSE-MsgGUID: HVskA2wXR2WOzdEVmKNImg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,314,1728975600"; d="scan'208";a="104876000" Received: from xiaoyaol-hp-g830.ccr.corp.intel.com (HELO [10.124.247.1]) ([10.124.247.1]) by orviesa006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jan 2025 04:39:40 -0800 Message-ID: <1b03e7a4-c398-4646-9182-e3757f65980e@intel.com> Date: Tue, 14 Jan 2025 20:39:37 +0800 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 09/60] i386/tdx: Initialize TDX before creating TD vcpus To: Tony Lindgren , Ira Weiny Cc: "Edgecombe, Rick P" , "riku.voipio@iki.fi" , "imammedo@redhat.com" , "Liu, Zhao1" , "marcel.apfelbaum@gmail.com" , "anisinha@redhat.com" , "mst@redhat.com" , "pbonzini@redhat.com" , "richard.henderson@linaro.org" , "armbru@redhat.com" , "philmd@linaro.org" , "cohuck@redhat.com" , "mtosatti@redhat.com" , "eblake@redhat.com" , "qemu-devel@nongnu.org" , "kvm@vger.kernel.org" , "wangyanan55@huawei.com" , "berrange@redhat.com" References: <20241105062408.3533704-1-xiaoyao.li@intel.com> <20241105062408.3533704-10-xiaoyao.li@intel.com> <1235bac6ffe7be6662839adb2630c1a97d1cc4c5.camel@intel.com> Content-Language: en-US From: Xiaoyao Li In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 12/17/2024 9:10 PM, Tony Lindgren wrote: > On Thu, Dec 12, 2024 at 11:24:03AM -0600, Ira Weiny wrote: >> On Wed, Nov 06, 2024 at 07:13:56AM +0200, Tony Lindgren wrote: >>> On Wed, Nov 06, 2024 at 10:01:04AM +0800, Xiaoyao Li wrote: >>>> On 11/6/2024 4:51 AM, Edgecombe, Rick P wrote: >>>>> +Tony >>>>> >>>>> On Tue, 2024-11-05 at 01:23 -0500, Xiaoyao Li wrote: >>>>>> +int tdx_pre_create_vcpu(CPUState *cpu, Error **errp) >>>>>> +{ >>>>>> +    X86CPU *x86cpu = X86_CPU(cpu); >>>>>> +    CPUX86State *env = &x86cpu->env; >>>>>> +    g_autofree struct kvm_tdx_init_vm *init_vm = NULL; >>>>>> +    int r = 0; >>>>>> + >>>>>> +    QEMU_LOCK_GUARD(&tdx_guest->lock); >>>>>> +    if (tdx_guest->initialized) { >>>>>> +        return r; >>>>>> +    } >>>>>> + >>>>>> +    init_vm = g_malloc0(sizeof(struct kvm_tdx_init_vm) + >>>>>> +                        sizeof(struct kvm_cpuid_entry2) * KVM_MAX_CPUID_ENTRIES); >>>>>> + >>>>>> +    r = setup_td_xfam(x86cpu, errp); >>>>>> +    if (r) { >>>>>> +        return r; >>>>>> +    } >>>>>> + >>>>>> +    init_vm->cpuid.nent = kvm_x86_build_cpuid(env, init_vm->cpuid.entries, 0); >>>>>> +    tdx_filter_cpuid(&init_vm->cpuid); >>>>>> + >>>>>> +    init_vm->attributes = tdx_guest->attributes; >>>>>> +    init_vm->xfam = tdx_guest->xfam; >>>>>> + >>>>>> +    do { >>>>>> +        r = tdx_vm_ioctl(KVM_TDX_INIT_VM, 0, init_vm); >>>>>> +    } while (r == -EAGAIN); >>>>> >>>>> KVM_TDX_INIT_VM can also return EBUSY. This should check for it, or KVM should >>>>> standardize on one for both conditions. In KVM, both cases handle >>>>> TDX_RND_NO_ENTROPY, but one tries to save some of the initialization for the >>>>> next attempt. I don't know why userspace would need to differentiate between the >>>>> two cases though, which makes me think we should just change the KVM side. >>>> >>>> I remember I tested retrying on the two cases and no surprise showed. >>>> >>>> I agree to change KVM side to return -EAGAIN for the two cases. >>> >>> OK yeah let's patch KVM for it. >> >> Will the patch to KVM converge such that it is ok for qemu to loop forever? > > Hmm I don't think we should loop forever anywhere, the retries needed should > be only a few. Or what do you have in mind? "A few" seems not accurate. It depends on how heavy the RDRAND/RDSEED traffic from others are. IIRC, it gets > 10 0000 -EAGAIN before success when all the LPs in the system are doing RDRAND/RDSEED. Maybe a timeout? E.g., QEMU exits when it cannot move forward for a certain period. However, I'm not sure what value is reasonable for the timeout. > Regards, > > Tony