@@ -22,6 +22,7 @@
 #include <linux/firmware.h>
 #include <linux/gfp.h>
 #include <linux/cpufeature.h>
+#include <linux/sev-guest.h>
 
 #include <asm/smp.h>
 

@@ -1616,6 +1617,48 @@ int snp_guest_dbg_decrypt(struct sev_data_snp_dbg *data, int *error)
 }
 EXPORT_SYMBOL_GPL(snp_guest_dbg_decrypt);
 
+int snp_guest_ext_guest_request(struct sev_data_snp_guest_request *data,
+				unsigned long vaddr, unsigned long *npages, unsigned long *fw_err)
+{
+	unsigned long expected_npages;
+	struct sev_device *sev;
+	int rc;
+
+	if (!psp_master || !psp_master->sev_data)
+		return -ENODEV;
+
+	sev = psp_master->sev_data;
+
+	if (!sev->snp_inited)
+		return -EINVAL;
+
+	/*
+	 * Check if we have enough space to copy the certificate chain. Otherwise
+	 * return ERROR code defined in the GHCB specification.
+	 */
+	expected_npages = sev->snp_certs_len >> PAGE_SHIFT;
+	if (*npages < expected_npages) {
+		*npages = expected_npages;
+		*fw_err = SNP_GUEST_REQ_INVALID_LEN;
+		return -EINVAL;
+	}
+
+	rc = sev_do_cmd(SEV_CMD_SNP_GUEST_REQUEST, data, (int *)&fw_err);
+	if (rc)
+		return rc;
+
+	/* Copy the certificate blob */
+	if (sev->snp_certs_data) {
+		*npages = expected_npages;
+		memcpy((void *)vaddr, sev->snp_certs_data, *npages << PAGE_SHIFT);
+	} else {
+		*npages = 0;
+	}
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(snp_guest_ext_guest_request);
+
 static void sev_exit(struct kref *ref)
 {
 	misc_deregister(&misc_dev->misc);

@@ -925,6 +925,23 @@ void *psp_copy_user_blob(u64 uaddr, u32 len);
 void *snp_alloc_firmware_page(gfp_t mask);
 void snp_free_firmware_page(void *addr);
 
+/**
+ * snp_guest_ext_guest_request - perform the SNP extended guest request command
+ *  defined in the GHCB specification.
+ *
+ * @data: the input guest request structure
+ * @vaddr: address where the certificate blob need to be copied.
+ * @npages: number of pages for the certificate blob.
+ *    If the specified page count is less than the certificate blob size, then the
+ *    required page count is returned with error code defined in the GHCB spec.
+ *    If the specified page count is more than the certificate blob size, then
+ *    page count is updated to reflect the amount of valid data copied in the
+ *    vaddr.
+ */
+int snp_guest_ext_guest_request(struct sev_data_snp_guest_request *data,
+				unsigned long vaddr, unsigned long *npages,
+				unsigned long *error);
+
 #else	/* !CONFIG_CRYPTO_DEV_SP_PSP */
 
 static inline int

@@ -972,6 +989,13 @@ static inline void *snp_alloc_firmware_page(gfp_t mask)
 
 static inline void snp_free_firmware_page(void *addr) { }
 
+static inline int snp_guest_ext_guest_request(struct sev_data_snp_guest_request *data,
+					      unsigned long vaddr, unsigned long *n,
+					      unsigned long *error)
+{
+	return -ENODEV;
+}
+
 #endif	/* CONFIG_CRYPTO_DEV_SP_PSP */
 
 #endif	/* __PSP_SEV_H__ */