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From:   Ashish Kalra <Ashish.Kalra@amd.com>
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Subject: [PATCH Part2 v6 46/49] ccp: add support to decrypt the page
Date:   Mon, 20 Jun 2022 23:14:43 +0000
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From: Brijesh Singh <brijesh.singh@amd.com>

Add support to decrypt guest encrypted memory, these API interfaces can be
used for example to dump VMCBs on SNP guest exit.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 drivers/crypto/ccp/sev-dev.c | 33 ++++++++++++++++++++++++++++++---
 include/linux/psp-sev.h      |  6 +++---
 2 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index f6306b820b86..9896350e7f56 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -1852,11 +1852,38 @@ int snp_guest_page_reclaim(struct sev_data_snp_page_reclaim *data, int *error)
 }
 EXPORT_SYMBOL_GPL(snp_guest_page_reclaim);
 
-int snp_guest_dbg_decrypt(struct sev_data_snp_dbg *data, int *error)
+int snp_guest_dbg_decrypt_page(u64 gctx_pfn, u64 src_pfn, u64 dst_pfn, int *error)
 {
-	return sev_do_cmd(SEV_CMD_SNP_DBG_DECRYPT, data, error);
+	struct sev_data_snp_dbg data = {0};
+	struct sev_device *sev;
+	int ret;
+
+	if (!psp_master || !psp_master->sev_data)
+		return -ENODEV;
+
+	sev = psp_master->sev_data;
+
+	if (!sev->snp_inited)
+		return -EINVAL;
+
+	data.gctx_paddr = sme_me_mask | (gctx_pfn << PAGE_SHIFT);
+	data.src_addr = sme_me_mask | (src_pfn << PAGE_SHIFT);
+	data.dst_addr = sme_me_mask | (dst_pfn << PAGE_SHIFT);
+	data.len = PAGE_SIZE;
+
+	/* The destination page must be in the firmware state. */
+	if (snp_set_rmp_state(data.dst_addr, 1, true, false, false))
+		return -EIO;
+
+	ret = sev_do_cmd(SEV_CMD_SNP_DBG_DECRYPT, &data, error);
+
+	/* Restore the page state */
+	if (snp_set_rmp_state(data.dst_addr, 1, false, false, true))
+		ret = -EIO;
+
+	return ret;
 }
-EXPORT_SYMBOL_GPL(snp_guest_dbg_decrypt);
+EXPORT_SYMBOL_GPL(snp_guest_dbg_decrypt_page);
 
 int snp_guest_ext_guest_request(struct sev_data_snp_guest_request *data,
 				unsigned long vaddr, unsigned long *npages, unsigned long *fw_err)
diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
index cd37ccd1fa1f..8d2565c70c39 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -928,7 +928,7 @@ int snp_guest_decommission(struct sev_data_snp_decommission *data, int *error);
 int snp_guest_page_reclaim(struct sev_data_snp_page_reclaim *data, int *error);
 
 /**
- * snp_guest_dbg_decrypt - perform SEV SNP_DBG_DECRYPT command
+ * snp_guest_dbg_decrypt_page - perform SEV SNP_DBG_DECRYPT command
  *
  * @sev_ret: sev command return code
  *
@@ -939,7 +939,7 @@ int snp_guest_page_reclaim(struct sev_data_snp_page_reclaim *data, int *error);
  * -%ETIMEDOUT if the sev command timed out
  * -%EIO       if the sev returned a non-zero return code
  */
-int snp_guest_dbg_decrypt(struct sev_data_snp_dbg *data, int *error);
+int snp_guest_dbg_decrypt_page(u64 gctx_pfn, u64 src_pfn, u64 dst_pfn, int *error);
 
 void *psp_copy_user_blob(u64 uaddr, u32 len);
 void *snp_alloc_firmware_page(gfp_t mask);
@@ -997,7 +997,7 @@ static inline int snp_guest_page_reclaim(struct sev_data_snp_page_reclaim *data,
 	return -ENODEV;
 }
 
-static inline int snp_guest_dbg_decrypt(struct sev_data_snp_dbg *data, int *error)
+static inline int snp_guest_dbg_decrypt_page(u64 gctx_pfn, u64 src_pfn, u64 dst_pfn, int *error)
 {
 	return -ENODEV;
 }
-- 
2.25.1