linux-kernel - Re: [PATCH v10 48/50] KVM: SEV: Provide support for SNP_GUEST

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4f8bb755-e208-fd8c-f948-f7d64260f8a7@amd.com>
Date:   Wed, 18 Oct 2023 16:27:15 -0500
From:   "Kalra, Ashish" <ashish.kalra@....com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Alexey Kardashevskiy <aik@....com>,
        Dionna Amalie Glaze <dionnaglaze@...gle.com>,
        Michael Roth <michael.roth@....com>, kvm@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        jroedel@...e.de, thomas.lendacky@....com, hpa@...or.com,
        ardb@...nel.org, pbonzini@...hat.com, vkuznets@...hat.com,
        jmattson@...gle.com, luto@...nel.org, dave.hansen@...ux.intel.com,
        slp@...hat.com, pgonda@...gle.com, peterz@...radead.org,
        srinivas.pandruvada@...ux.intel.com, rientjes@...gle.com,
        dovmurik@...ux.ibm.com, tobin@....com, bp@...en8.de,
        vbabka@...e.cz, kirill@...temov.name, ak@...ux.intel.com,
        tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, alpergun@...gle.com,
        jarkko@...nel.org, nikunj.dadhania@....com, pankaj.gupta@....com,
        liam.merwick@...cle.com, zhi.a.wang@...el.com,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v10 48/50] KVM: SEV: Provide support for SNP_GUEST_REQUEST
 NAE event


On 10/18/2023 3:38 PM, Sean Christopherson wrote:
> On Wed, Oct 18, 2023, Ashish Kalra wrote:
>>> static int snp_handle_ext_guest_request(struct vcpu_svm *svm)
>>> {
>>> 	struct kvm_vcpu *vcpu = &svm->vcpu;
>>> 	struct kvm *kvm = vcpu->kvm;
>>> 	struct kvm_sev_info *sev;
>>> 	unsigned long exitcode;
>>> 	u64 data_gpa;
>>>
>>> 	if (!sev_snp_guest(vcpu->kvm)) {
>>> 		ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, SEV_RET_INVALID_GUEST);
>>> 		return 1;
>>> 	}
>>>
>>> 	data_gpa = vcpu->arch.regs[VCPU_REGS_RAX];
>>> 	if (!IS_ALIGNED(data_gpa, PAGE_SIZE)) {
>>> 		ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, SEV_RET_INVALID_ADDRESS);
>>> 		return 1;
>>> 	}
>>>
>>> 	vcpu->run->hypercall.nr		 = KVM_HC_SNP_GET_CERTS;
>>> 	vcpu->run->hypercall.args[0]	 = data_gpa;
>>> 	vcpu->run->hypercall.args[1]	 = vcpu->arch.regs[VCPU_REGS_RBX];
>>> 	vcpu->run->hypercall.flags	 = KVM_EXIT_HYPERCALL_LONG_MODE;
>>> 	vcpu->arch.complete_userspace_io = snp_complete_ext_guest_request;
>>> 	return 0;
>>> }
>>>
>>
>> IIRC, the important consideration here is to ensure that getting the
>> attestation report and retrieving the certificates appears atomic to the
>> guest. When SNP live migration is supported we don't want a case where the
>> guest could have migrated between the call to obtain the certificates and
>> obtaining the attestation report, which can potentially cause failure of
>> validation of the attestation report.
> 
> Where does "obtaining the attestation report" happen?  I see the guest request
> and the certificate stuff, I don't see anything about attestation reports (though
> I'm not looking very closely).
> 

The guest requests that the firmware construct an attestation report via 
the SNP_GUEST_REQUEST command. The certificates are piggy-backed to the 
guest along with the attestation report (retrieved from the FW via the 
SNP_GUEST_REQUEST command) as part of the SNP Extended Guest Request NAE 
handling.

Thanks,
Ashish