[PATCH v1 20/26] crypto: ccp: Add debug support for decrypting pages

Michael Roth
2023-12-30T16:25:58Z

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>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
[mdr: minor commit fixups]
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
drivers/crypto/ccp/sev-dev.c | 32 ++++++++++++++++++++++++++++++++
include/linux/psp-sev.h | 19 +++++++++++++++++++
2 files changed, 51 insertions(+)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 47fc58ed9e6a..9792c7af3005 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -2053,6 +2053,38 @@ int sev_guest_df_flush(int *error)
}
EXPORT_SYMBOL_GPL(sev_guest_df_flush);

+int snp_guest_dbg_decrypt_page(u64 gctx_pfn, u64 src_pfn, u64 dst_pfn, int *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_initialized)
+ 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);
+
+ /* The destination page must be in the firmware state. */
+ if (rmp_mark_pages_firmware(data.dst_addr, 1, false))
+ return -EIO;
+
+ ret = sev_do_cmd(SEV_CMD_SNP_DBG_DECRYPT, &data, error);
+
+ /* Restore the page state */
+ if (snp_reclaim_pages(data.dst_addr, 1, false))
+ ret = -EIO;
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(snp_guest_dbg_decrypt_page);
+
static void sev_exit(struct kref *ref)
{
misc_deregister(&misc_dev->misc);
diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
index 16d0da895680..b14008388a37 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -930,6 +930,20 @@ int sev_guest_decommission(struct sev_data_decommission *data, int *error);
*/
int sev_do_cmd(int cmd, void *data, int *psp_ret);

+/**
+ * snp_guest_dbg_decrypt_page - perform SEV SNP_DBG_DECRYPT command
+ *
+ * @sev_ret: sev command return code
+ *
+ * Returns:
+ * 0 if the SEV successfully processed the command
+ * -%ENODEV if the SEV device is not available
+ * -%ENOTSUPP if the SEV does not support SEV
+ * -%ETIMEDOUT if the SEV command timed out
+ * -%EIO if the SEV returned a non-zero return code
+ */
+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);
void snp_free_firmware_page(void *addr);
@@ -960,6 +974,11 @@ sev_issue_cmd_external_user(struct file *filep, unsigned int id, void *data, int

static inline void *psp_copy_user_blob(u64 __user uaddr, u32 len) { return ERR_PTR(-EINVAL); }

+static inline int snp_guest_dbg_decrypt_page(u64 gctx_pfn, u64 src_pfn, u64 dst_pfn, int *error)
+{
+ return -ENODEV;
+}
+
static inline void *snp_alloc_firmware_page(gfp_t mask)
{
return NULL;
--
2.25.1