Messages in this thread Patch in this message | | | Date | Tue, 10 Jan 2023 13:28:05 +1100 | Subject | Re: [PATCH RFC v7 52/64] KVM: SVM: Provide support for SNP_GUEST_REQUEST NAE event | From | Alexey Kardashevskiy <> |
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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@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.
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,
> 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 { >>
-- Alexey
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