[Qemu-devel] [PATCH 1/2] pc: acpi: use correct RSDT length for checksum

[Igor Mammedov <imammedo@redhat.com>]

AcpiRsdpDescriptor describes revision 2 RSDP table so using sizeof(*rsdp)
for checksum calculation isn't correct since we are adding extra 16 bytes.
But acpi_data_push() zeroes out table, so just by luck we are summing up
exta zeros which still yelds correct checksum.

Fix it up by explicitly stating table size instead of using
pointer arithmetics on stucture.

PS:
Extra 16 bytes are still wasted, but droping them will break migration
for machines older than 2.3 due to size mismatch, for 2.3 and older it's
not an issue since they are using resizable memory regions (a1666142d)
for ACPI blobs. So keep wasting memory to avoid breaking old machines.

Fixes: 72c194f7e (i386: ACPI table generation code from seabios)
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
there is no changes to the current RSDP content caused by this patch
---
 hw/i386/acpi-build.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 236a20e..131c565 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -2567,7 +2567,7 @@ build_rsdp(GArray *rsdp_table, BIOSLinker *linker, unsigned rsdt_tbl_offset)
 
     /* Checksum to be filled by Guest linker */
     bios_linker_loader_add_checksum(linker, ACPI_BUILD_RSDP_FILE,
-        (char *)rsdp - rsdp_table->data, sizeof *rsdp,
+        (char *)rsdp - rsdp_table->data, 20 /* ACPI rev 1.0 RSDP size */,
         (char *)&rsdp->checksum - rsdp_table->data);
 
     return rsdp_table;
-- 
2.7.4