Merge tag 'x86_urgent_for_v6.3_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Borislav Petkov:
 "There's a little bit more 'movement' in there for my taste but it
  needs to happen and should make the code better after it.

   - Check cmdline_find_option()'s return value before further
     processing

   - Clear temporary storage in the resctrl code to prevent access to an
     unexistent MSR

   - Add a simple throttling mechanism to protect the hypervisor from
     potentially malicious SEV guests issuing requests in rapid
     succession.

     In order to not jeopardize the sanity of everyone involved in
     maintaining this code, the request issuing side has received a
     cleanup, split in more or less trivial, small and digestible
     pieces. Otherwise, the code was threatening to become an
     unmaintainable mess.

     Therefore, that cleanup is marked indirectly also for stable so
     that there's no differences between the upstream code and the
     stable variant when it comes down to backporting more there"

* tag 'x86_urgent_for_v6.3_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/mm: Fix use of uninitialized buffer in sme_enable()
  x86/resctrl: Clear staged_config[] before and after it is used
  virt/coco/sev-guest: Add throttling awareness
  virt/coco/sev-guest: Convert the sw_exit_info_2 checking to a switch-case
  virt/coco/sev-guest: Do some code style cleanups
  virt/coco/sev-guest: Carve out the request issuing logic into a helper
  virt/coco/sev-guest: Remove the disable_vmpck label in handle_guest_request()
  virt/coco/sev-guest: Simplify extended guest request handling
  virt/coco/sev-guest: Check SEV_SNP attribute at probe time

7 files changed, 123 insertions, 70 deletions

diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
index b8357d6ecd47..b63be696b776 100644
--- a/arch/x86/include/asm/sev-common.h
+++ b/arch/x86/include/asm/sev-common.h
@@ -128,8 +128,9 @@ struct snp_psc_desc {
 	struct psc_entry entries[VMGEXIT_PSC_MAX_ENTRY];
 } __packed;
 
-/* Guest message request error code */
+/* Guest message request error codes */
 #define SNP_GUEST_REQ_INVALID_LEN	BIT_ULL(32)
+#define SNP_GUEST_REQ_ERR_BUSY		BIT_ULL(33)
 
 #define GHCB_MSR_TERM_REQ		0x100
 #define GHCB_MSR_TERM_REASON_SET_POS	12
diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index eb07d4435391..b44c487727d4 100644
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -368,7 +368,6 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
 {
 	struct resctrl_schema *s;
 	struct rdtgroup *rdtgrp;
-	struct rdt_domain *dom;
 	struct rdt_resource *r;
 	char *tok, *resname;
 	int ret = 0;
@@ -397,10 +396,7 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
 		goto out;
 	}
 
-	list_for_each_entry(s, &resctrl_schema_all, list) {
-		list_for_each_entry(dom, &s->res->domains, list)
-			memset(dom->staged_config, 0, sizeof(dom->staged_config));
-	}
+	rdt_staged_configs_clear();
 
 	while ((tok = strsep(&buf, "\n")) != NULL) {
 		resname = strim(strsep(&tok, ":"));
@@ -445,6 +441,7 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
 	}
 
 out:
+	rdt_staged_configs_clear();
 	rdtgroup_kn_unlock(of->kn);
 	cpus_read_unlock();
 	return ret ?: nbytes;
diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
index 8edecc5763d8..85ceaf9a31ac 100644
--- a/arch/x86/kernel/cpu/resctrl/internal.h
+++ b/arch/x86/kernel/cpu/resctrl/internal.h
@@ -555,5 +555,6 @@ void __check_limbo(struct rdt_domain *d, bool force_free);
 void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
 void __init thread_throttle_mode_init(void);
 void __init mbm_config_rftype_init(const char *config);
+void rdt_staged_configs_clear(void);
 
 #endif /* _ASM_X86_RESCTRL_INTERNAL_H */
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 884b6e9a7e31..6ad33f355861 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -78,6 +78,19 @@ void rdt_last_cmd_printf(const char *fmt, ...)
 	va_end(ap);
 }
 
+void rdt_staged_configs_clear(void)
+{
+	struct rdt_resource *r;
+	struct rdt_domain *dom;
+
+	lockdep_assert_held(&rdtgroup_mutex);
+
+	for_each_alloc_capable_rdt_resource(r) {
+		list_for_each_entry(dom, &r->domains, list)
+			memset(dom->staged_config, 0, sizeof(dom->staged_config));
+	}
+}
+
 /*
  * Trivial allocator for CLOSIDs. Since h/w only supports a small number,
  * we can keep a bitmap of free CLOSIDs in a single integer.
@@ -3107,7 +3120,9 @@ static int rdtgroup_init_alloc(struct rdtgroup *rdtgrp)
 {
 	struct resctrl_schema *s;
 	struct rdt_resource *r;
-	int ret;
+	int ret = 0;
+
+	rdt_staged_configs_clear();
 
 	list_for_each_entry(s, &resctrl_schema_all, list) {
 		r = s->res;
@@ -3119,20 +3134,22 @@ static int rdtgroup_init_alloc(struct rdtgroup *rdtgrp)
 		} else {
 			ret = rdtgroup_init_cat(s, rdtgrp->closid);
 			if (ret < 0)
-				return ret;
+				goto out;
 		}
 
 		ret = resctrl_arch_update_domains(r, rdtgrp->closid);
 		if (ret < 0) {
 			rdt_last_cmd_puts("Failed to initialize allocations\n");
-			return ret;
+			goto out;
 		}
 
 	}
 
 	rdtgrp->mode = RDT_MODE_SHAREABLE;
 
-	return 0;
+out:
+	rdt_staged_configs_clear();
+	return ret;
 }
 
 static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 679026a640ef..3f664ab277c4 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -2183,9 +2183,6 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned
 	struct ghcb *ghcb;
 	int ret;
 
-	if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
-		return -ENODEV;
-
 	if (!fw_err)
 		return -EINVAL;
 
@@ -2212,15 +2209,26 @@ int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned
 	if (ret)
 		goto e_put;
 
-	if (ghcb->save.sw_exit_info_2) {
-		/* Number of expected pages are returned in RBX */
-		if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST &&
-		    ghcb->save.sw_exit_info_2 == SNP_GUEST_REQ_INVALID_LEN)
-			input->data_npages = ghcb_get_rbx(ghcb);
+	*fw_err = ghcb->save.sw_exit_info_2;
+	switch (*fw_err) {
+	case 0:
+		break;
 
-		*fw_err = ghcb->save.sw_exit_info_2;
+	case SNP_GUEST_REQ_ERR_BUSY:
+		ret = -EAGAIN;
+		break;
 
+	case SNP_GUEST_REQ_INVALID_LEN:
+		/* Number of expected pages are returned in RBX */
+		if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST) {
+			input->data_npages = ghcb_get_rbx(ghcb);
+			ret = -ENOSPC;
+			break;
+		}
+		fallthrough;
+	default:
 		ret = -EIO;
+		break;
 	}
 
 e_put:
diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c
index 88cccd65029d..c6efcf559d88 100644
--- a/arch/x86/mm/mem_encrypt_identity.c
+++ b/arch/x86/mm/mem_encrypt_identity.c
@@ -600,7 +600,8 @@ void __init sme_enable(struct boot_params *bp)
 	cmdline_ptr = (const char *)((u64)bp->hdr.cmd_line_ptr |
 				     ((u64)bp->ext_cmd_line_ptr << 32));
 
-	cmdline_find_option(cmdline_ptr, cmdline_arg, buffer, sizeof(buffer));
+	if (cmdline_find_option(cmdline_ptr, cmdline_arg, buffer, sizeof(buffer)) < 0)
+		return;
 
 	if (!strncmp(buffer, cmdline_on, sizeof(buffer)))
 		sme_me_mask = me_mask;
diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 7b4e9009f335..46f1a8d558b0 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -31,6 +31,9 @@
 #define AAD_LEN		48
 #define MSG_HDR_VER	1
 
+#define SNP_REQ_MAX_RETRY_DURATION	(60*HZ)
+#define SNP_REQ_RETRY_DELAY		(2*HZ)
+
 struct snp_guest_crypto {
 	struct crypto_aead *tfm;
 	u8 *iv, *authtag;
@@ -318,26 +321,14 @@ static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8
 	return __enc_payload(snp_dev, req, payload, sz);
 }
 
-static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
-				u8 type, void *req_buf, size_t req_sz, void *resp_buf,
-				u32 resp_sz, __u64 *fw_err)
+static int __handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, __u64 *fw_err)
 {
-	unsigned long err;
-	u64 seqno;
+	unsigned long err = 0xff, override_err = 0;
+	unsigned long req_start = jiffies;
+	unsigned int override_npages = 0;
 	int rc;
 
-	/* Get message sequence and verify that its a non-zero */
-	seqno = snp_get_msg_seqno(snp_dev);
-	if (!seqno)
-		return -EIO;
-
-	memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
-
-	/* Encrypt the userspace provided payload */
-	rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
-	if (rc)
-		return rc;
-
+retry_request:
 	/*
 	 * Call firmware to process the request. In this function the encrypted
 	 * message enters shared memory with the host. So after this call the
@@ -345,18 +336,24 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 	 * prevent reuse of the IV.
 	 */
 	rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
+	switch (rc) {
+	case -ENOSPC:
+		/*
+		 * If the extended guest request fails due to having too
+		 * small of a certificate data buffer, retry the same
+		 * guest request without the extended data request in
+		 * order to increment the sequence number and thus avoid
+		 * IV reuse.
+		 */
+		override_npages = snp_dev->input.data_npages;
+		exit_code	= SVM_VMGEXIT_GUEST_REQUEST;
 
-	/*
-	 * If the extended guest request fails due to having too small of a
-	 * certificate data buffer, retry the same guest request without the
-	 * extended data request in order to increment the sequence number
-	 * and thus avoid IV reuse.
-	 */
-	if (exit_code == SVM_VMGEXIT_EXT_GUEST_REQUEST &&
-	    err == SNP_GUEST_REQ_INVALID_LEN) {
-		const unsigned int certs_npages = snp_dev->input.data_npages;
-
-		exit_code = SVM_VMGEXIT_GUEST_REQUEST;
+		/*
+		 * Override the error to inform callers the given extended
+		 * request buffer size was too small and give the caller the
+		 * required buffer size.
+		 */
+		override_err	= SNP_GUEST_REQ_INVALID_LEN;
 
 		/*
 		 * If this call to the firmware succeeds, the sequence number can
@@ -366,15 +363,20 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 		 * of the VMPCK and the error code being propagated back to the
 		 * user as an ioctl() return code.
 		 */
-		rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
+		goto retry_request;
 
-		/*
-		 * Override the error to inform callers the given extended
-		 * request buffer size was too small and give the caller the
-		 * required buffer size.
-		 */
-		err = SNP_GUEST_REQ_INVALID_LEN;
-		snp_dev->input.data_npages = certs_npages;
+	/*
+	 * The host may return SNP_GUEST_REQ_ERR_EBUSY if the request has been
+	 * throttled. Retry in the driver to avoid returning and reusing the
+	 * message sequence number on a different message.
+	 */
+	case -EAGAIN:
+		if (jiffies - req_start > SNP_REQ_MAX_RETRY_DURATION) {
+			rc = -ETIMEDOUT;
+			break;
+		}
+		schedule_timeout_killable(SNP_REQ_RETRY_DELAY);
+		goto retry_request;
 	}
 
 	/*
@@ -386,7 +388,10 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 	snp_inc_msg_seqno(snp_dev);
 
 	if (fw_err)
-		*fw_err = err;
+		*fw_err = override_err ?: err;
+
+	if (override_npages)
+		snp_dev->input.data_npages = override_npages;
 
 	/*
 	 * If an extended guest request was issued and the supplied certificate
@@ -394,29 +399,49 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, in
 	 * prevent IV reuse. If the standard request was successful, return -EIO
 	 * back to the caller as would have originally been returned.
 	 */
-	if (!rc && err == SNP_GUEST_REQ_INVALID_LEN)
+	if (!rc && override_err == SNP_GUEST_REQ_INVALID_LEN)
+		return -EIO;
+
+	return rc;
+}
+
+static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
+				u8 type, void *req_buf, size_t req_sz, void *resp_buf,
+				u32 resp_sz, __u64 *fw_err)
+{
+	u64 seqno;
+	int rc;
+
+	/* Get message sequence and verify that its a non-zero */
+	seqno = snp_get_msg_seqno(snp_dev);
+	if (!seqno)
 		return -EIO;
 
+	memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
+
+	/* Encrypt the userspace provided payload */
+	rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
+	if (rc)
+		return rc;
+
+	rc = __handle_guest_request(snp_dev, exit_code, fw_err);
 	if (rc) {
-		dev_alert(snp_dev->dev,
-			  "Detected error from ASP request. rc: %d, fw_err: %llu\n",
-			  rc, *fw_err);
-		goto disable_vmpck;
+		if (rc == -EIO && *fw_err == SNP_GUEST_REQ_INVALID_LEN)
+			return rc;
+
+		dev_alert(snp_dev->dev, "Detected error from ASP request. rc: %d, fw_err: %llu\n", rc, *fw_err);
+		snp_disable_vmpck(snp_dev);
+		return rc;
 	}
 
 	rc = verify_and_dec_payload(snp_dev, resp_buf, resp_sz);
 	if (rc) {
-		dev_alert(snp_dev->dev,
-			  "Detected unexpected decode failure from ASP. rc: %d\n",
-			  rc);
-		goto disable_vmpck;
+		dev_alert(snp_dev->dev, "Detected unexpected decode failure from ASP. rc: %d\n", rc);
+		snp_disable_vmpck(snp_dev);
+		return rc;
 	}
 
 	return 0;
-
-disable_vmpck:
-	snp_disable_vmpck(snp_dev);
-	return rc;
 }
 
 static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
@@ -703,6 +728,9 @@ static int __init sev_guest_probe(struct platform_device *pdev)
 	void __iomem *mapping;
 	int ret;
 
+	if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
+		return -ENODEV;
+
 	if (!dev->platform_data)
 		return -ENODEV;