hw/i386/pc: pc_system_ovmf_table_find: Assert that flash was parsed

Add assertion in pc_system_ovmf_table_find that verifies that the flash
was indeed previously parsed (looking for the OVMF table) by
pc_system_parse_ovmf_flash.

Now pc_system_ovmf_table_find distinguishes between "no one called
pc_system_parse_ovmf_flash" (which will abort due to assertion failure)
and "the flash was parsed but no OVMF table was found, or it is invalid"
(which will return false).

Suggested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20210701052749.934744-2-dovmurik@linux.ibm.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

hw/i386/pc_sysfw.c

@@ -126,6 +126,7 @@ void pc_system_flash_cleanup_unused(PCMachineState *pcms)
 
 #define OVMF_TABLE_FOOTER_GUID "96b582de-1fb2-45f7-baea-a366c55a082d"
 
+static bool ovmf_flash_parsed;
 static uint8_t *ovmf_table;
 static int ovmf_table_len;
 
@@ -136,10 +137,12 @@ static void pc_system_parse_ovmf_flash(uint8_t *flash_ptr, size_t flash_size)
     int tot_len;
 
     /* should only be called once */
-    if (ovmf_table) {
+    if (ovmf_flash_parsed) {
         return;
     }
 
+    ovmf_flash_parsed = true;
+
     if (flash_size < TARGET_PAGE_SIZE) {
         return;
     }
@@ -183,6 +186,8 @@ bool pc_system_ovmf_table_find(const char *entry, uint8_t **data,
     int tot_len = ovmf_table_len;
     QemuUUID entry_guid;
 
+    assert(ovmf_flash_parsed);
+
     if (qemu_uuid_parse(entry, &entry_guid) < 0) {
         return false;
     }