[PATCH v3 40/49] hw/i386/sev: Add function to get SEV metadata from OVMF header

[Michael Roth <michael.roth@xxxxxxx>]

From: Brijesh Singh <brijesh.singh@xxxxxxx>

A recent version of OVMF expanded the reset vector GUID list to add
SEV-specific metadata GUID. The SEV metadata describes the reserved
memory regions such as the secrets and CPUID page used during the SEV-SNP
guest launch.

The pc_system_get_ovmf_sev_metadata_ptr() is used to retieve the SEV
metadata pointer from the OVMF GUID list.

Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
---
 hw/i386/pc_sysfw_ovmf.c | 33 +++++++++++++++++++++++++++++++++
 include/hw/i386/pc.h    | 26 ++++++++++++++++++++++++++
 2 files changed, 59 insertions(+)

diff --git a/hw/i386/pc_sysfw_ovmf.c b/hw/i386/pc_sysfw_ovmf.c
index 07a4c267fa..32efa34614 100644
--- a/hw/i386/pc_sysfw_ovmf.c
+++ b/hw/i386/pc_sysfw_ovmf.c
@@ -35,6 +35,31 @@ static const int bytes_after_table_footer = 32;
 static bool ovmf_flash_parsed;
 static uint8_t *ovmf_table;
 static int ovmf_table_len;
+static OvmfSevMetadata *ovmf_sev_metadata_table;
+
+#define OVMF_SEV_META_DATA_GUID "dc886566-984a-4798-A75e-5585a7bf67cc"
+typedef struct __attribute__((__packed__)) OvmfSevMetadataOffset {
+    uint32_t offset;
+} OvmfSevMetadataOffset;
+
+static void pc_system_parse_sev_metadata(uint8_t *flash_ptr, size_t flash_size)
+{
+    OvmfSevMetadata     *metadata;
+    OvmfSevMetadataOffset  *data;
+
+    if (!pc_system_ovmf_table_find(OVMF_SEV_META_DATA_GUID, (uint8_t **)&data,
+                                   NULL)) {
+        return;
+    }
+
+    metadata = (OvmfSevMetadata *)(flash_ptr + flash_size - data->offset);
+    if (memcmp(metadata->signature, "ASEV", 4) != 0) {
+        return;
+    }
+
+    ovmf_sev_metadata_table = g_malloc(metadata->len);
+    memcpy(ovmf_sev_metadata_table, metadata, metadata->len);
+}
 
 void pc_system_parse_ovmf_flash(uint8_t *flash_ptr, size_t flash_size)
 {
@@ -90,6 +115,9 @@ void pc_system_parse_ovmf_flash(uint8_t *flash_ptr, size_t flash_size)
      */
     memcpy(ovmf_table, ptr - tot_len, tot_len);
     ovmf_table += tot_len;
+
+    /* Copy the SEV metadata table (if exist) */
+    pc_system_parse_sev_metadata(flash_ptr, flash_size);
 }
 
 /**
@@ -159,3 +187,8 @@ bool pc_system_ovmf_table_find(const char *entry, uint8_t **data,
     }
     return false;
 }
+
+OvmfSevMetadata *pc_system_get_ovmf_sev_metadata_ptr(void)
+{
+    return ovmf_sev_metadata_table;
+}
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index fb1d4106e5..df9a61540d 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -163,6 +163,32 @@ void pc_acpi_smi_interrupt(void *opaque, int irq, int level);
 #define PCI_HOST_ABOVE_4G_MEM_SIZE     "above-4g-mem-size"
 #define PCI_HOST_PROP_SMM_RANGES       "smm-ranges"
 
+typedef enum {
+    SEV_DESC_TYPE_UNDEF,
+    /* The section contains the region that must be validated by the VMM. */
+    SEV_DESC_TYPE_SNP_SEC_MEM,
+    /* The section contains the SNP secrets page */
+    SEV_DESC_TYPE_SNP_SECRETS,
+    /* The section contains address that can be used as a CPUID page */
+    SEV_DESC_TYPE_CPUID,
+
+} ovmf_sev_metadata_desc_type;
+
+typedef struct __attribute__((__packed__)) OvmfSevMetadataDesc {
+    uint32_t base;
+    uint32_t len;
+    ovmf_sev_metadata_desc_type type;
+} OvmfSevMetadataDesc;
+
+typedef struct __attribute__((__packed__)) OvmfSevMetadata {
+    uint8_t signature[4];
+    uint32_t len;
+    uint32_t version;
+    uint32_t num_desc;
+    OvmfSevMetadataDesc descs[];
+} OvmfSevMetadata;
+
+OvmfSevMetadata *pc_system_get_ovmf_sev_metadata_ptr(void);
 
 void pc_pci_as_mapping_init(MemoryRegion *system_memory,
                             MemoryRegion *pci_address_space);
-- 
2.25.1