On Thu, Nov 22, 2018 at 11:29:33AM +0100, Igor Mammedov wrote: > 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.
I'd like this explanation in code comments please. > Fixes: 72c194f7e (i386: ACPI table generation code from seabios) > Signed-off-by: Igor Mammedov <imamm...@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; I dislike hard-coded size math like this. How about a sub-structure for RSDPv1? > -- > 2.7.4
