Date:   Tue, 31 Jan 2023 11:52:30 -0600
From:   "Kalra, Ashish" <ashish.kalra@....com>
To:     Alexey Kardashevskiy <aik@....com>,
        Michael Roth <michael.roth@....com>, kvm@...r.kernel.org
Cc:     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, seanjc@...gle.com,
        vkuznets@...hat.com, wanpengli@...cent.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,
        dgilbert@...hat.com, jarkko@...nel.org, harald@...fian.com,
        Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH RFC v7 52/64] KVM: SVM: Provide support for
 SNP_GUEST_REQUEST NAE event

On 1/30/2023 7:54 PM, Alexey Kardashevskiy wrote:
> 
> 
> On 11/1/23 13:01, Kalra, Ashish wrote:
>> On 1/10/2023 6:48 PM, Alexey Kardashevskiy wrote:
>>> On 10/1/23 19:33, Kalra, Ashish wrote:
>>>>
>>>> On 1/9/2023 8:28 PM, Alexey Kardashevskiy wrote:
>>>>>
>>>>>
>>>>> On 10/1/23 10:41, Kalra, Ashish wrote:
>>>>>> On 1/8/2023 9:33 PM, Alexey Kardashevskiy wrote:
>>>>>>> On 15/12/22 06:40, Michael Roth wrote:
>>>>>>>> From: Brijesh Singh <brijesh.singh@....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@....com>
>>>>>>>> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
>>>>>>>> Signed-off-by: Michael Roth <michael.roth@....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.
>>>>>
>>>>> True. I thought though that this calls for extending 
>>>>> sev_issue_cmd() to take care of these extra parameters rather than 
>>>>> just skipping the sev->fd.
>>>>>
>>>>>
>>>>>> 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.
>>>>>
>>>>> Does not look like it:
>>>>>
>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/crypto/ccp/sev-dev.c?h=v6.2-rc3#n1290 
>>>>>
>>>>>
>>>>> ===
>>>>> int sev_issue_cmd_external_user(struct file *filep, unsigned int cmd,
>>>>>                  void *data, int *error)
>>>>> {
>>>>>      if (!filep || filep->f_op != &sev_fops)
>>>>>          return -EBADF;
>>>>>
>>>>>      return sev_do_cmd(cmd, data, error);
>>>>> }
>>>>> EXPORT_SYMBOL_GPL(sev_issue_cmd_external_user);
>>>>> ===
>>>>>
>>>>> The only "more" is that it requires sev->fd to be a valid open fd, 
>>>>> what is the value in that? I may easily miss the bigger picture 
>>>>> here. Thanks,
>>>>>
>>>>>
>>>>
>>>> Have a look at following functions in drivers/crypto/ccp/sev-dev.c:
>>>> sev_dev_init() and sev_misc_init().
>>>>
>>>> static int sev_misc_init(struct sev_device *sev)
>>>> {
>>>>          struct device *dev = sev->dev;
>>>>          int ret;
>>>>
>>>>          /*
>>>>           * SEV feature support can be detected on multiple devices but
>>>>           * the SEV FW commands must be issued on the master. During
>>>>           * probe, we do not know the master hence we create 
>>>> /dev/sev on
>>>>           * the first device probe.
>>>>           * sev_do_cmd() finds the right master device to which to 
>>>> issue
>>>>           * the command to the firmware.
>>>>       */
>>>
>>>
>>> It is still a single /dev/sev node and the userspace cannot get it 
>>> wrong, it does not have to choose between (for instance) /dev/sev0 
>>> and /dev/sev1 on a 2 SOC system.
>>>
>>>> ...
>>>> ...
>>>>
>>>> Hence, sev_issue_cmd_external_user() needs to ensure that the 
>>>> correct device (master device) is being operated upon and that's why 
>>>> there is the check for file operations matching sev_fops as below :
>>>>
>>>> int sev_issue_cmd_external_user(struct file *filep, unsigned int cmd,
>>>>                                  void *data, int *error)
>>>> {
>>>>          if (!filep || filep->f_op != &sev_fops)
>>>>                  return -EBADF;
>>>> ..
>>>> ..
>>>>
>>>> Essentially, sev->fd is the misc. device created for the master PSP 
>>>> device on which the SEV/SNP firmware commands are issued, hence,
>>>> sev_issue_cmd() uses sev->fd.
>>>
>>> There is always just one fd which always uses psp_master, nothing 
>>> from that fd is used.
>>
>> It also ensures that we can only issue commands (sev_issue_cmd) after 
>> SEV/SNP guest has launched.
> 
> I can open /dev/sev and start sending commands to the firmware with no 
> KVM running at all. Oh well, we discussed this offline :)
> 

Yes, and as we already discussed we need to support that to get SEV/SNP 
platform status (SNP_PLATFORM_STATUS) and also for legacy SEV commands 
like certificate generation and import/export which can be issued before 
a VM is launched.

Thanks,
Ashish

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