Re: [PATCH RFC v7 52/64] KVM: SVM: Provide support for SNP_GUEST_REQUEST NAE event

From: "Kalra, Ashish" <ashish.kalra@amd.com>
To: Alexey Kardashevskiy <aik@amd.com>,
	Michael Roth <michael.roth@amd.com>,
	kvm@vger.kernel.org
Cc: linux-coco@lists.linux.dev, linux-mm@kvack.org,
	linux-crypto@vger.kernel.org, x86@kernel.org,
	linux-kernel@vger.kernel.org, tglx@linutronix.de,
	mingo@redhat.com, jroedel@suse.de, thomas.lendacky@amd.com,
	hpa@zytor.com, ardb@kernel.org, pbonzini@redhat.com,
	seanjc@google.com, vkuznets@redhat.com, wanpengli@tencent.com,
	jmattson@google.com, luto@kernel.org,
	dave.hansen@linux.intel.com, slp@redhat.com, pgonda@google.com,
	peterz@infradead.org, srinivas.pandruvada@linux.intel.com,
	rientjes@google.com, dovmurik@linux.ibm.com, tobin@ibm.com,
	bp@alien8.de, vbabka@suse.cz, kirill@shutemov.name,
	ak@linux.intel.com, tony.luck@intel.com, marcorr@google.com,
	sathyanarayanan.kuppuswamy@linux.intel.com, alpergun@google.com,
	dgilbert@redhat.com, jarkko@kernel.org, harald@profian.com,
	Brijesh Singh <brijesh.singh@amd.com>
Subject: Re: [PATCH RFC v7 52/64] KVM: SVM: Provide support for SNP_GUEST_REQUEST NAE event
Date: Mon, 9 Jan 2023 17:41:07 -0600	[thread overview]
Message-ID: <66039193-14ca-5edb-d8d4-ca732d8c13a6@amd.com> (raw)
In-Reply-To: <aab7ed11-870e-579d-9328-4c32d9936392@amd.com>

On 1/8/2023 9:33 PM, Alexey Kardashevskiy wrote:
> On 15/12/22 06:40, Michael Roth wrote:
>> From: Brijesh Singh <brijesh.singh@amd.com>
>>
>> Version 2 of GHCB specification added the support for two SNP Guest
>> Request Message NAE events. The events allows for an SEV-SNP guest to
>> make request to the SEV-SNP firmware through hypervisor using the
>> SNP_GUEST_REQUEST API define in the SEV-SNP firmware specification.
>>
>> The SNP_EXT_GUEST_REQUEST is similar to SNP_GUEST_REQUEST with the
>> difference of an additional certificate blob that can be passed through
>> the SNP_SET_CONFIG ioctl defined in the CCP driver. The CCP driver
>> provides snp_guest_ext_guest_request() that is used by the KVM to get
>> both the report and certificate data at once.
>>
>> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
>> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
>> Signed-off-by: Michael Roth <michael.roth@amd.com>
>> ---
>>   arch/x86/kvm/svm/sev.c | 185 +++++++++++++++++++++++++++++++++++++++--
>>   arch/x86/kvm/svm/svm.h |   2 +
>>   2 files changed, 181 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
>> index 5f2b2092cdae..18efa70553c2 100644
>> --- a/arch/x86/kvm/svm/sev.c
>> +++ b/arch/x86/kvm/svm/sev.c
>> @@ -331,6 +331,7 @@ static int sev_guest_init(struct kvm *kvm, struct 
>> kvm_sev_cmd *argp)
>>           if (ret)
>>               goto e_free;
>> +        mutex_init(&sev->guest_req_lock);
>>           ret = sev_snp_init(&argp->error, false);
>>       } else {
>>           ret = sev_platform_init(&argp->error);
>> @@ -2051,23 +2052,34 @@ int sev_vm_move_enc_context_from(struct kvm 
>> *kvm, unsigned int source_fd)
>>    */
>>   static void *snp_context_create(struct kvm *kvm, struct kvm_sev_cmd 
>> *argp)
>>   {
>> +    struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
>>       struct sev_data_snp_addr data = {};
>> -    void *context;
>> +    void *context, *certs_data;
>>       int rc;
>> +    /* Allocate memory used for the certs data in SNP guest request */
>> +    certs_data = kzalloc(SEV_FW_BLOB_MAX_SIZE, GFP_KERNEL_ACCOUNT);
>> +    if (!certs_data)
>> +        return NULL;
>> +
>>       /* Allocate memory for context page */
>>       context = snp_alloc_firmware_page(GFP_KERNEL_ACCOUNT);
>>       if (!context)
>> -        return NULL;
>> +        goto e_free;
>>       data.gctx_paddr = __psp_pa(context);
>>       rc = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_GCTX_CREATE, 
>> &data, &argp->error);
>> -    if (rc) {
>> -        snp_free_firmware_page(context);
>> -        return NULL;
>> -    }
>> +    if (rc)
>> +        goto e_free;
>> +
>> +    sev->snp_certs_data = certs_data;
>>       return context;
>> +
>> +e_free:
>> +    snp_free_firmware_page(context);
>> +    kfree(certs_data);
>> +    return NULL;
>>   }
>>   static int snp_bind_asid(struct kvm *kvm, int *error)
>> @@ -2653,6 +2665,8 @@ static int snp_decommission_context(struct kvm 
>> *kvm)
>>       snp_free_firmware_page(sev->snp_context);
>>       sev->snp_context = NULL;
>> +    kfree(sev->snp_certs_data);
>> +
>>       return 0;
>>   }
>> @@ -3174,6 +3188,8 @@ static int sev_es_validate_vmgexit(struct 
>> vcpu_svm *svm, u64 *exit_code)
>>       case SVM_VMGEXIT_UNSUPPORTED_EVENT:
>>       case SVM_VMGEXIT_HV_FEATURES:
>>       case SVM_VMGEXIT_PSC:
>> +    case SVM_VMGEXIT_GUEST_REQUEST:
>> +    case SVM_VMGEXIT_EXT_GUEST_REQUEST:
>>           break;
>>       default:
>>           reason = GHCB_ERR_INVALID_EVENT;
>> @@ -3396,6 +3412,149 @@ static int snp_complete_psc(struct kvm_vcpu 
>> *vcpu)
>>       return 1;
>>   }
>> +static unsigned long snp_setup_guest_buf(struct vcpu_svm *svm,
>> +                     struct sev_data_snp_guest_request *data,
>> +                     gpa_t req_gpa, gpa_t resp_gpa)
>> +{
>> +    struct kvm_vcpu *vcpu = &svm->vcpu;
>> +    struct kvm *kvm = vcpu->kvm;
>> +    kvm_pfn_t req_pfn, resp_pfn;
>> +    struct kvm_sev_info *sev;
>> +
>> +    sev = &to_kvm_svm(kvm)->sev_info;
>> +
>> +    if (!IS_ALIGNED(req_gpa, PAGE_SIZE) || !IS_ALIGNED(resp_gpa, 
>> PAGE_SIZE))
>> +        return SEV_RET_INVALID_PARAM;
>> +
>> +    req_pfn = gfn_to_pfn(kvm, gpa_to_gfn(req_gpa));
>> +    if (is_error_noslot_pfn(req_pfn))
>> +        return SEV_RET_INVALID_ADDRESS;
>> +
>> +    resp_pfn = gfn_to_pfn(kvm, gpa_to_gfn(resp_gpa));
>> +    if (is_error_noslot_pfn(resp_pfn))
>> +        return SEV_RET_INVALID_ADDRESS;
>> +
>> +    if (rmp_make_private(resp_pfn, 0, PG_LEVEL_4K, 0, true))
>> +        return SEV_RET_INVALID_ADDRESS;
>> +
>> +    data->gctx_paddr = __psp_pa(sev->snp_context);
>> +    data->req_paddr = __sme_set(req_pfn << PAGE_SHIFT);
>> +    data->res_paddr = __sme_set(resp_pfn << PAGE_SHIFT);
>> +
>> +    return 0;
>> +}
>> +
>> +static void snp_cleanup_guest_buf(struct sev_data_snp_guest_request 
>> *data, unsigned long *rc)
>> +{
>> +    u64 pfn = __sme_clr(data->res_paddr) >> PAGE_SHIFT;
>> +    int ret;
>> +
>> +    ret = snp_page_reclaim(pfn);
>> +    if (ret)
>> +        *rc = SEV_RET_INVALID_ADDRESS;
>> +
>> +    ret = rmp_make_shared(pfn, PG_LEVEL_4K);
>> +    if (ret)
>> +        *rc = SEV_RET_INVALID_ADDRESS;
>> +}
>> +
>> +static void snp_handle_guest_request(struct vcpu_svm *svm, gpa_t 
>> req_gpa, gpa_t resp_gpa)
>> +{
>> +    struct sev_data_snp_guest_request data = {0};
>> +    struct kvm_vcpu *vcpu = &svm->vcpu;
>> +    struct kvm *kvm = vcpu->kvm;
>> +    struct kvm_sev_info *sev;
>> +    unsigned long rc;
>> +    int err;
>> +
>> +    if (!sev_snp_guest(vcpu->kvm)) {
>> +        rc = SEV_RET_INVALID_GUEST;
>> +        goto e_fail;
>> +    }
>> +
>> +    sev = &to_kvm_svm(kvm)->sev_info;
>> +
>> +    mutex_lock(&sev->guest_req_lock);
>> +
>> +    rc = snp_setup_guest_buf(svm, &data, req_gpa, resp_gpa);
>> +    if (rc)
>> +        goto unlock;
>> +
>> +    rc = sev_issue_cmd(kvm, SEV_CMD_SNP_GUEST_REQUEST, &data, &err);
> 
> 
> This one goes via sev_issue_cmd_external_user() and uses sev-fd...
> 
>> +    if (rc)
>> +        /* use the firmware error code */
>> +        rc = err;
>> +
>> +    snp_cleanup_guest_buf(&data, &rc);
>> +
>> +unlock:
>> +    mutex_unlock(&sev->guest_req_lock);
>> +
>> +e_fail:
>> +    svm_set_ghcb_sw_exit_info_2(vcpu, rc);
>> +}
>> +
>> +static void snp_handle_ext_guest_request(struct vcpu_svm *svm, gpa_t 
>> req_gpa, gpa_t resp_gpa)
>> +{
>> +    struct sev_data_snp_guest_request req = {0};
>> +    struct kvm_vcpu *vcpu = &svm->vcpu;
>> +    struct kvm *kvm = vcpu->kvm;
>> +    unsigned long data_npages;
>> +    struct kvm_sev_info *sev;
>> +    unsigned long rc, err;
>> +    u64 data_gpa;
>> +
>> +    if (!sev_snp_guest(vcpu->kvm)) {
>> +        rc = SEV_RET_INVALID_GUEST;
>> +        goto e_fail;
>> +    }
>> +
>> +    sev = &to_kvm_svm(kvm)->sev_info;
>> +
>> +    data_gpa = vcpu->arch.regs[VCPU_REGS_RAX];
>> +    data_npages = vcpu->arch.regs[VCPU_REGS_RBX];
>> +
>> +    if (!IS_ALIGNED(data_gpa, PAGE_SIZE)) {
>> +        rc = SEV_RET_INVALID_ADDRESS;
>> +        goto e_fail;
>> +    }
>> +
>> +    mutex_lock(&sev->guest_req_lock);
>> +
>> +    rc = snp_setup_guest_buf(svm, &req, req_gpa, resp_gpa);
>> +    if (rc)
>> +        goto unlock;
>> +
>> +    rc = snp_guest_ext_guest_request(&req, (unsigned 
>> long)sev->snp_certs_data,
>> +                     &data_npages, &err);
> 
> but this one does not and jump straight to drivers/crypto/ccp/sev-dev.c 
> ignoring sev->fd. Why different? Can these two be unified? 
> sev_issue_cmd_external_user() only checks if fd is /dev/sev which is 
> hardly useful.
> 
> "[PATCH RFC v7 32/64] crypto: ccp: Provide APIs to query extended 
> attestation report" added this one.

SNP_EXT_GUEST_REQUEST additionally returns a certificate blob and that's 
why it goes through the CCP driver interface 
snp_guest_ext_guest_request() that is used to get both the report and 
certificate data/blob at the same time.

All the FW API calls on the KVM side go through sev_issue_cmd() and 
sev_issue_cmd_external_user() interfaces and that i believe uses sev->fd 
more of as a sanity check.

Thanks,
Ashish

> 
> Besides, is sev->fd really needed in the sev struct at all? Thanks,
> 
> 
>> +    if (rc) {
>> +        /*
>> +         * If buffer length is small then return the expected
>> +         * length in rbx.
>> +         */
>> +        if (err == SNP_GUEST_REQ_INVALID_LEN)
>> +            vcpu->arch.regs[VCPU_REGS_RBX] = data_npages;
>> +
>> +        /* pass the firmware error code */
>> +        rc = err;
>> +        goto cleanup;
>> +    }
>> +
>> +    /* Copy the certificate blob in the guest memory */
>> +    if (data_npages &&
>> +        kvm_write_guest(kvm, data_gpa, sev->snp_certs_data, 
>> data_npages << PAGE_SHIFT))
>> +        rc = SEV_RET_INVALID_ADDRESS;
>> +
>> +cleanup:
>> +    snp_cleanup_guest_buf(&req, &rc);
>> +
>> +unlock:
>> +    mutex_unlock(&sev->guest_req_lock);
>> +
>> +e_fail:
>> +    svm_set_ghcb_sw_exit_info_2(vcpu, rc);
>> +}
>> +
>>   static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
>>   {
>>       struct vmcb_control_area *control = &svm->vmcb->control;
>> @@ -3629,6 +3788,20 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
>>           vcpu->run->vmgexit.ghcb_msr = ghcb_gpa;
>>           vcpu->arch.complete_userspace_io = snp_complete_psc;
>>           break;
>> +    case SVM_VMGEXIT_GUEST_REQUEST: {
>> +        snp_handle_guest_request(svm, control->exit_info_1, 
>> control->exit_info_2);
>> +
>> +        ret = 1;
>> +        break;
>> +    }
>> +    case SVM_VMGEXIT_EXT_GUEST_REQUEST: {
>> +        snp_handle_ext_guest_request(svm,
>> +                         control->exit_info_1,
>> +                         control->exit_info_2);
>> +
>> +        ret = 1;
>> +        break;
>> +    }
>>       case SVM_VMGEXIT_UNSUPPORTED_EVENT:
>>           vcpu_unimpl(vcpu,
>>                   "vmgexit: unsupported event - exit_info_1=%#llx, 
>> exit_info_2=%#llx\n",
>> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
>> index 12b9f4d539fb..7c0f9d00950f 100644
>> --- a/arch/x86/kvm/svm/svm.h
>> +++ b/arch/x86/kvm/svm/svm.h
>> @@ -101,6 +101,8 @@ struct kvm_sev_info {
>>       u64 snp_init_flags;
>>       void *snp_context;      /* SNP guest context page */
>>       spinlock_t psc_lock;
>> +    void *snp_certs_data;
>> +    struct mutex guest_req_lock;
>>   };
>>   struct kvm_svm {
> 