[Qemu-devel] [RFC PATCH v1 14/22] sev: provide SEV-enabled guest RAM read/write ops

[Brijesh Singh]

The patch implements kvm_sev_get_ram_ops() which provides guest RAM
read/write callback. Depending on the memory attributes and guest launch
state, the callback will use SEV launch update or SEV debug commands
to read/write into guest memory.

Signed-off-by: Brijesh Singh <brijesh.si...@amd.com>
---
 include/sysemu/sev.h |    8 ++++++++
 sev.c                |   46 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/include/sysemu/sev.h b/include/sysemu/sev.h
index e8fa62f..ec2dfde 100644
--- a/include/sysemu/sev.h
+++ b/include/sysemu/sev.h
@@ -15,6 +15,7 @@
 #define QEMU_SEV_H
 
 #include "sysemu/kvm.h"
+#include "exec/memory.h"
 
 typedef enum SevState {
     SEV_STATE_INVALID = 0x0,
@@ -93,4 +94,11 @@ int kvm_sev_dbg_encrypt(uint8_t *dest, const uint8_t *src, 
uint32_t len);
  */
 int kvm_sev_get_status(SevState *state, char *str);
 
+/*
+ * kvm_sev_get_ram_ops - get MemoryRegionRW ops.
+ *
+ * Return NULL on failure.
+ */
+MemoryRegionRAMReadWriteOps *kvm_sev_get_ram_ops(void);
+
 #endif
diff --git a/sev.c b/sev.c
index 508eff2..c1135c4 100644
--- a/sev.c
+++ b/sev.c
@@ -72,6 +72,8 @@ typedef struct SEVInfo SEVInfo;
 static SEVInfo *sev_info;
 static const char *cfg_file;
 
+static MemoryRegionRAMReadWriteOps sev_ops;
+
 enum {
     LAUNCH_OPTS = 0,
 };
@@ -512,3 +514,47 @@ int kvm_sev_get_status(SevState *state, char *msg)
             sev_state_msg[*state]);
     return 0;
 }
+
+static inline int sev_read(uint8_t *dst, const uint8_t *src,
+                           uint32_t len, MemTxAttrs attrs)
+{
+    if (attrs.sev_debug) {
+        return kvm_sev_dbg_decrypt(dst, src, len);
+    }
+
+    memcpy(dst, src, len);
+    return 0;
+}
+
+static inline int sev_write(uint8_t *dst, const uint8_t *src,
+                            uint32_t len, MemTxAttrs attrs)
+{
+    SEVInfo *s = sev_info;
+
+    /* If we are in SEV launch stage then use launch_update command
+     * to copy and encrypt the data into guest memory.
+     */
+    if (s->state == SEV_LAUNCH_START) {
+        memcpy(dst, src, len);               /* copy data into guest memory */
+        return sev_launch_update(dst, len);  /* encrypt the data in-place */
+    }
+
+    if (attrs.sev_debug) {
+        return kvm_sev_dbg_encrypt(dst, src, len);
+    }
+
+    memcpy(dst, src, len);
+    return 0;
+}
+
+MemoryRegionRAMReadWriteOps *kvm_sev_get_ram_ops(void)
+{
+    if (!sev_info) {
+        return NULL;
+    }
+
+    sev_ops.read = sev_read;
+    sev_ops.write = sev_write;
+
+    return &sev_ops;
+}