Merge tag 'kvm-x86-ciphertext-6.18' of https://github.com/kvm-x86/linux into HEAD

KVM SEV-SNP CipherText Hiding support for 6.18

Add support for SEV-SNP's CipherText Hiding, an opt-in feature that prevents
unauthorized CPU accesses from reading the ciphertext of SNP guest private
memory, e.g. to attempt an offline attack. Instead of ciphertext, the CPU
will always read back all FFs when CipherText Hiding is enabled.

Add new module parameter to the KVM module to enable CipherText Hiding and
control the number of ASIDs that can be used for VMs with CipherText Hiding,
which is in effect the number of SNP VMs. When CipherText Hiding is enabled,
the shared SEV-ES/SEV-SNP ASID space is split into separate ranges for SEV-ES
and SEV-SNP guests, i.e. ASIDs that can be used for CipherText Hiding cannot
be used to run SEV-ES guests.

Documentation/admin-guide/kernel-parameters.txt

···
 			(enabled). Disable by KVM if hardware lacks support
 			for NPT.
 
+	kvm-amd.ciphertext_hiding_asids=
+			[KVM,AMD] Ciphertext hiding prevents disallowed accesses
+			to SNP private memory from reading ciphertext.  Instead,
+			reads will see constant default values (0xff).
+
+			If ciphertext hiding is enabled, the joint SEV-ES and
+			SEV-SNP ASID space is partitioned into separate SEV-ES
+			and SEV-SNP ASID ranges, with the SEV-SNP range being
+			[1..max_snp_asid] and the SEV-ES range being
+			(max_snp_asid..min_sev_asid), where min_sev_asid is
+			enumerated by CPUID.0x.8000_001F[EDX].
+
+			A non-zero value enables SEV-SNP ciphertext hiding and
+			adjusts the ASID ranges for SEV-ES and SEV-SNP guests.
+			KVM caps the number of SEV-SNP ASIDs at the maximum
+			possible value, e.g. specifying -1u will assign all
+			joint SEV-ES and SEV-SNP ASIDs to SEV-SNP.  Note,
+			assigning all joint ASIDs to SEV-SNP, i.e. configuring
+			max_snp_asid == min_sev_asid-1, will effectively make
+			SEV-ES unusable.
+
 	kvm-arm.mode=
 			[KVM,ARM,EARLY] Select one of KVM/arm64's modes of
 			operation.

arch/x86/kvm/svm/sev.c

···
 module_param_named(debug_swap, sev_es_debug_swap_enabled, bool, 0444);
 static u64 sev_supported_vmsa_features;
 
+static unsigned int nr_ciphertext_hiding_asids;
+module_param_named(ciphertext_hiding_asids, nr_ciphertext_hiding_asids, uint, 0444);
+
 #define AP_RESET_HOLD_NONE		0
 #define AP_RESET_HOLD_NAE_EVENT		1
 #define AP_RESET_HOLD_MSR_PROTO		2
···
 static DEFINE_MUTEX(sev_bitmap_lock);
 unsigned int max_sev_asid;
 static unsigned int min_sev_asid;
+static unsigned int max_sev_es_asid;
+static unsigned int min_sev_es_asid;
+static unsigned int max_snp_asid;
+static unsigned int min_snp_asid;
 static unsigned long sev_me_mask;
 static unsigned int nr_asids;
 static unsigned long *sev_asid_bitmap;
···
 	misc_cg_uncharge(type, sev->misc_cg, 1);
 }
 
-static int sev_asid_new(struct kvm_sev_info *sev)
+static int sev_asid_new(struct kvm_sev_info *sev, unsigned long vm_type)
 {
 	/*
 	 * SEV-enabled guests must use asid from min_sev_asid to max_sev_asid.
 	 * SEV-ES-enabled guest can use from 1 to min_sev_asid - 1.
-	 * Note: min ASID can end up larger than the max if basic SEV support is
-	 * effectively disabled by disallowing use of ASIDs for SEV guests.
 	 */
-	unsigned int min_asid = sev->es_active ? 1 : min_sev_asid;
-	unsigned int max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid;
-	unsigned int asid;
+	unsigned int min_asid, max_asid, asid;
 	bool retry = true;
 	int ret;
 
+	if (vm_type == KVM_X86_SNP_VM) {
+		min_asid = min_snp_asid;
+		max_asid = max_snp_asid;
+	} else if (sev->es_active) {
+		min_asid = min_sev_es_asid;
+		max_asid = max_sev_es_asid;
+	} else {
+		min_asid = min_sev_asid;
+		max_asid = max_sev_asid;
+	}
+
+	/*
+	 * The min ASID can end up larger than the max if basic SEV support is
+	 * effectively disabled by disallowing use of ASIDs for SEV guests.
+	 * Similarly for SEV-ES guests the min ASID can end up larger than the
+	 * max when ciphertext hiding is enabled, effectively disabling SEV-ES
+	 * support.
+	 */
 	if (min_asid > max_asid)
 		return -ENOTTY;
 
···
 	if (snp_active)
 		sev->vmsa_features |= SVM_SEV_FEAT_SNP_ACTIVE;
 
-	ret = sev_asid_new(sev);
+	ret = sev_asid_new(sev, vm_type);
 	if (ret)
 		goto e_no_asid;
 
···
 	if (min_sev_asid == 1)
 		goto out;
 
+	min_sev_es_asid = min_snp_asid = 1;
+	max_sev_es_asid = max_snp_asid = min_sev_asid - 1;
+
 	sev_es_asid_count = min_sev_asid - 1;
 	WARN_ON_ONCE(misc_cg_set_capacity(MISC_CG_RES_SEV_ES, sev_es_asid_count));
 	sev_es_supported = true;
···
 out:
 	if (sev_enabled) {
 		init_args.probe = true;
+
+		if (sev_is_snp_ciphertext_hiding_supported())
+			init_args.max_snp_asid = min(nr_ciphertext_hiding_asids,
+						     min_sev_asid - 1);
+
 		if (sev_platform_init(&init_args))
 			sev_supported = sev_es_supported = sev_snp_supported = false;
 		else if (sev_snp_supported)
 			sev_snp_supported = is_sev_snp_initialized();
+
+		if (sev_snp_supported)
+			nr_ciphertext_hiding_asids = init_args.max_snp_asid;
+
+		/*
+		 * If ciphertext hiding is enabled, the joint SEV-ES/SEV-SNP
+		 * ASID range is partitioned into separate SEV-ES and SEV-SNP
+		 * ASID ranges, with the SEV-SNP range being [1..max_snp_asid]
+		 * and the SEV-ES range being (max_snp_asid..max_sev_es_asid].
+		 * Note, SEV-ES may effectively be disabled if all ASIDs from
+		 * the joint range are assigned to SEV-SNP.
+		 */
+		if (nr_ciphertext_hiding_asids) {
+			max_snp_asid = nr_ciphertext_hiding_asids;
+			min_sev_es_asid = max_snp_asid + 1;
+			pr_info("SEV-SNP ciphertext hiding enabled\n");
+		}
 	}
 
 	if (boot_cpu_has(X86_FEATURE_SEV))
···
 			min_sev_asid, max_sev_asid);
 	if (boot_cpu_has(X86_FEATURE_SEV_ES))
 		pr_info("SEV-ES %s (ASIDs %u - %u)\n",
-			str_enabled_disabled(sev_es_supported),
-			min_sev_asid > 1 ? 1 : 0, min_sev_asid - 1);
+			sev_es_supported ? min_sev_es_asid <= max_sev_es_asid ? "enabled" :
+										"unusable" :
+										"disabled",
+			min_sev_es_asid, max_sev_es_asid);
 	if (boot_cpu_has(X86_FEATURE_SEV_SNP))
 		pr_info("SEV-SNP %s (ASIDs %u - %u)\n",
 			str_enabled_disabled(sev_snp_supported),
-			min_sev_asid > 1 ? 1 : 0, min_sev_asid - 1);
+			min_snp_asid, max_snp_asid);
 
 	sev_enabled = sev_supported;
 	sev_es_enabled = sev_es_supported;

drivers/crypto/ccp/sev-dev.c

···
 	case SEV_CMD_SNP_GUEST_REQUEST:		return sizeof(struct sev_data_snp_guest_request);
 	case SEV_CMD_SNP_CONFIG:		return sizeof(struct sev_user_data_snp_config);
 	case SEV_CMD_SNP_COMMIT:		return sizeof(struct sev_data_snp_commit);
+	case SEV_CMD_SNP_FEATURE_INFO:		return sizeof(struct sev_data_snp_feature_info);
 	default:				return 0;
 	}
 
···
 	wrmsrq(MSR_VM_HSAVE_PA, 0);
 }
 
+bool sev_is_snp_ciphertext_hiding_supported(void)
+{
+	struct psp_device *psp = psp_master;
+	struct sev_device *sev;
+
+	if (!psp || !psp->sev_data)
+		return false;
+
+	sev = psp->sev_data;
+
+	/*
+	 * Feature information indicates if CipherTextHiding feature is
+	 * supported by the SEV firmware and additionally platform status
+	 * indicates if CipherTextHiding feature is enabled in the
+	 * Platform BIOS.
+	 */
+	return ((sev->snp_feat_info_0.ecx & SNP_CIPHER_TEXT_HIDING_SUPPORTED) &&
+		 sev->snp_plat_status.ciphertext_hiding_cap);
+}
+EXPORT_SYMBOL_GPL(sev_is_snp_ciphertext_hiding_supported);
+
+static int snp_get_platform_data(struct sev_device *sev, int *error)
+{
+	struct sev_data_snp_feature_info snp_feat_info;
+	struct snp_feature_info *feat_info;
+	struct sev_data_snp_addr buf;
+	struct page *page;
+	int rc;
+
+	/*
+	 * This function is expected to be called before SNP is
+	 * initialized.
+	 */
+	if (sev->snp_initialized)
+		return -EINVAL;
+
+	buf.address = __psp_pa(&sev->snp_plat_status);
+	rc = sev_do_cmd(SEV_CMD_SNP_PLATFORM_STATUS, &buf, error);
+	if (rc) {
+		dev_err(sev->dev, "SNP PLATFORM_STATUS command failed, ret = %d, error = %#x\n",
+			rc, *error);
+		return rc;
+	}
+
+	sev->api_major = sev->snp_plat_status.api_major;
+	sev->api_minor = sev->snp_plat_status.api_minor;
+	sev->build = sev->snp_plat_status.build_id;
+
+	/*
+	 * Do feature discovery of the currently loaded firmware,
+	 * and cache feature information from CPUID 0x8000_0024,
+	 * sub-function 0.
+	 */
+	if (!sev->snp_plat_status.feature_info)
+		return 0;
+
+	/*
+	 * Use dynamically allocated structure for the SNP_FEATURE_INFO
+	 * command to ensure structure is 8-byte aligned, and does not
+	 * cross a page boundary.
+	 */
+	page = alloc_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+
+	feat_info = page_address(page);
+	snp_feat_info.length = sizeof(snp_feat_info);
+	snp_feat_info.ecx_in = 0;
+	snp_feat_info.feature_info_paddr = __psp_pa(feat_info);
+
+	rc = sev_do_cmd(SEV_CMD_SNP_FEATURE_INFO, &snp_feat_info, error);
+	if (!rc)
+		sev->snp_feat_info_0 = *feat_info;
+	else
+		dev_err(sev->dev, "SNP FEATURE_INFO command failed, ret = %d, error = %#x\n",
+			rc, *error);
+
+	__free_page(page);
+
+	return rc;
+}
+
 static int snp_filter_reserved_mem_regions(struct resource *rs, void *arg)
 {
 	struct sev_data_range_list *range_list = arg;
···
 	return 0;
 }
 
-static int __sev_snp_init_locked(int *error)
+static int __sev_snp_init_locked(int *error, unsigned int max_snp_asid)
 {
 	struct psp_device *psp = psp_master;
 	struct sev_data_snp_init_ex data;
···
 		}
 
 		memset(&data, 0, sizeof(data));
+
+		if (max_snp_asid) {
+			data.ciphertext_hiding_en = 1;
+			data.max_snp_asid = max_snp_asid;
+		}
+
 		data.init_rmp = 1;
 		data.list_paddr_en = 1;
 		data.list_paddr = __psp_pa(snp_range_list);
···
 
 	sev = psp_master->sev_data;
 
-	if (sev->state == SEV_STATE_INIT)
+	if (sev->sev_plat_status.state == SEV_STATE_INIT)
 		return 0;
 
 	__sev_platform_init_handle_tmr(sev);
···
 		return rc;
 	}
 
-	sev->state = SEV_STATE_INIT;
+	sev->sev_plat_status.state = SEV_STATE_INIT;
 
 	/* Prepare for first SEV guest launch after INIT */
 	wbinvd_on_all_cpus();
···
 
 	sev = psp_master->sev_data;
 
-	if (sev->state == SEV_STATE_INIT)
+	if (sev->sev_plat_status.state == SEV_STATE_INIT)
 		return 0;
 
-	rc = __sev_snp_init_locked(&args->error);
+	rc = __sev_snp_init_locked(&args->error, args->max_snp_asid);
 	if (rc && rc != -ENODEV)
 		return rc;
 
···
 
 	sev = psp->sev_data;
 
-	if (sev->state == SEV_STATE_UNINIT)
+	if (sev->sev_plat_status.state == SEV_STATE_UNINIT)
 		return 0;
 
 	ret = __sev_do_cmd_locked(SEV_CMD_SHUTDOWN, NULL, error);
···
 		return ret;
 	}
 
-	sev->state = SEV_STATE_UNINIT;
+	sev->sev_plat_status.state = SEV_STATE_UNINIT;
 	dev_dbg(sev->dev, "SEV firmware shutdown\n");
 
 	return ret;
···
 {
 	int error, rc;
 
-	rc = __sev_snp_init_locked(&error);
+	rc = __sev_snp_init_locked(&error, 0);
 	if (rc) {
 		argp->error = SEV_RET_INVALID_PLATFORM_STATE;
 		return rc;
···
 	if (!writable)
 		return -EPERM;
 
-	if (sev->state == SEV_STATE_UNINIT) {
+	if (sev->sev_plat_status.state == SEV_STATE_UNINIT) {
 		rc = sev_move_to_init_state(argp, &shutdown_required);
 		if (rc)
 			return rc;
···
 	data.len = input.length;
 
 cmd:
-	if (sev->state == SEV_STATE_UNINIT) {
+	if (sev->sev_plat_status.state == SEV_STATE_UNINIT) {
 		ret = sev_move_to_init_state(argp, &shutdown_required);
 		if (ret)
 			goto e_free_blob;
···
 	struct sev_user_data_status status;
 	int error = 0, ret;
 
+	/*
+	 * Cache SNP platform status and SNP feature information
+	 * if SNP is available.
+	 */
+	if (cc_platform_has(CC_ATTR_HOST_SEV_SNP)) {
+		ret = snp_get_platform_data(sev, &error);
+		if (ret)
+			return 1;
+	}
+
 	ret = sev_platform_status(&status, &error);
 	if (ret) {
 		dev_err(sev->dev,
···
 		return 1;
 	}
 
+	/* Cache SEV platform status */
+	sev->sev_plat_status = status;
+
 	sev->api_major = status.api_major;
 	sev->api_minor = status.api_minor;
 	sev->build = status.build;
-	sev->state = status.state;
 
 	return 0;
 }
···
 	data.oca_cert_len = input.oca_cert_len;
 
 	/* If platform is not in INIT state then transition it to INIT */
-	if (sev->state != SEV_STATE_INIT) {
+	if (sev->sev_plat_status.state != SEV_STATE_INIT) {
 		ret = sev_move_to_init_state(argp, &shutdown_required);
 		if (ret)
 			goto e_free_oca;
···
 
 cmd:
 	/* If platform is not in INIT state then transition it to INIT. */
-	if (sev->state != SEV_STATE_INIT) {
+	if (sev->sev_plat_status.state != SEV_STATE_INIT) {
 		if (!writable) {
 			ret = -EPERM;
 			goto e_free_cert;

drivers/crypto/ccp/sev-dev.h

···
 
 	struct sev_vdata *vdata;
 
-	int state;
 	unsigned int int_rcvd;
 	wait_queue_head_t int_queue;
 	struct sev_misc_dev *misc;
···
 	bool cmd_buf_backup_active;
 
 	bool snp_initialized;
+
+	struct sev_user_data_status sev_plat_status;
+
+	struct sev_user_data_snp_status snp_plat_status;
+	struct snp_feature_info snp_feat_info_0;
 };
 
 int sev_dev_init(struct psp_device *psp);

include/linux/psp-sev.h

···
 	SEV_CMD_SNP_DOWNLOAD_FIRMWARE_EX = 0x0CA,
 	SEV_CMD_SNP_COMMIT		= 0x0CB,
 	SEV_CMD_SNP_VLEK_LOAD		= 0x0CD,
+	SEV_CMD_SNP_FEATURE_INFO	= 0x0CE,
 
 	SEV_CMD_MAX,
 };
···
 struct sev_data_snp_init_ex {
 	u32 init_rmp:1;
 	u32 list_paddr_en:1;
-	u32 rsvd:30;
+	u32 rapl_dis:1;
+	u32 ciphertext_hiding_en:1;
+	u32 rsvd:28;
 	u32 rsvd1;
 	u64 list_paddr;
-	u8  rsvd2[48];
+	u16 max_snp_asid;
+	u8  rsvd2[46];
 } __packed;
 
 /**
···
  * @probe: True if this is being called as part of CCP module probe, which
  *  will defer SEV_INIT/SEV_INIT_EX firmware initialization until needed
  *  unless psp_init_on_probe module param is set
+ * @max_snp_asid: When non-zero, enable ciphertext hiding and specify the
+ *  maximum ASID that can be used for an SEV-SNP guest.
  */
 struct sev_platform_init_args {
 	int error;
 	bool probe;
+	unsigned int max_snp_asid;
 };
 
 /**
···
 struct sev_data_snp_commit {
 	u32 len;
 } __packed;
+
+/**
+ * struct sev_data_snp_feature_info - SEV_SNP_FEATURE_INFO structure
+ *
+ * @length: len of the command buffer read by the PSP
+ * @ecx_in: subfunction index
+ * @feature_info_paddr : System Physical Address of the FEATURE_INFO structure
+ */
+struct sev_data_snp_feature_info {
+	u32 length;
+	u32 ecx_in;
+	u64 feature_info_paddr;
+} __packed;
+
+/**
+ * struct feature_info - FEATURE_INFO structure
+ *
+ * @eax: output of SNP_FEATURE_INFO command
+ * @ebx: output of SNP_FEATURE_INFO command
+ * @ecx: output of SNP_FEATURE_INFO command
+ * #edx: output of SNP_FEATURE_INFO command
+ */
+struct snp_feature_info {
+	u32 eax;
+	u32 ebx;
+	u32 ecx;
+	u32 edx;
+} __packed;
+
+#define SNP_CIPHER_TEXT_HIDING_SUPPORTED	BIT(3)
 
 #ifdef CONFIG_CRYPTO_DEV_SP_PSP
 
···
 void *snp_alloc_firmware_page(gfp_t mask);
 void snp_free_firmware_page(void *addr);
 void sev_platform_shutdown(void);
+bool sev_is_snp_ciphertext_hiding_supported(void);
 
 #else	/* !CONFIG_CRYPTO_DEV_SP_PSP */
 
···
 static inline void snp_free_firmware_page(void *addr) { }
 
 static inline void sev_platform_shutdown(void) { }
+
+static inline bool sev_is_snp_ciphertext_hiding_supported(void) { return false; }
 
 #endif	/* CONFIG_CRYPTO_DEV_SP_PSP */
 

include/uapi/linux/psp-sev.h

···
  * @mask_chip_id: whether chip id is present in attestation reports or not
  * @mask_chip_key: whether attestation reports are signed or not
  * @vlek_en: VLEK (Version Loaded Endorsement Key) hashstick is loaded
+ * @feature_info: whether SNP_FEATURE_INFO command is available
+ * @rapl_dis: whether RAPL is disabled
+ * @ciphertext_hiding_cap: whether platform has ciphertext hiding capability
+ * @ciphertext_hiding_en: whether ciphertext hiding is enabled
  * @rsvd1: reserved
  * @guest_count: the number of guest currently managed by the firmware
  * @current_tcb_version: current TCB version
···
 	__u32 mask_chip_id:1;		/* Out */
 	__u32 mask_chip_key:1;		/* Out */
 	__u32 vlek_en:1;		/* Out */
-	__u32 rsvd1:29;
+	__u32 feature_info:1;		/* Out */
+	__u32 rapl_dis:1;		/* Out */
+	__u32 ciphertext_hiding_cap:1;	/* Out */
+	__u32 ciphertext_hiding_en:1;	/* Out */
+	__u32 rsvd1:25;
 	__u32 guest_count;		/* Out */
 	__u64 current_tcb_version;	/* Out */
 	__u64 reported_tcb_version;	/* Out */