On 4/17/19 3:40 AM, Wei Yang wrote:
> From: Igor Mammedov <imamm...@redhat.com>
>
> Dummy table (with signature "QEMU") creation came from original SeaBIOS
> codebase. And QEMU would have to keep it around if there were Q35 machine
> that depended on keeping ACPI tables blob constant size. Luckily there
> were no versioned Q35 machine types before commit:
> (since 2.3) a1666142db acpi-build: make ROMs RAM blocks resizeable
> which obsoleted need to keep ACPI tables blob the same size on
> source/destination.
>
> Considering the 1st versioned machine is pc-q35-2.4, the dummy table
> is not really necessary and it's safe to drop it without breaking
> cross version migration in both directions unconditionally.
>
> Signed-off-by: Igor Mammedov <imamm...@redhat.com>
> Signed-off-by: Wei Yang <richardw.y...@linux.intel.com>
> ---
> hw/i386/acpi-build.c | 18 ++++--------------
> 1 file changed, 4 insertions(+), 14 deletions(-)
>
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index b17d4a711d..d009176072 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -2401,7 +2401,6 @@ static void
> build_mcfg_q35(GArray *table_data, BIOSLinker *linker, AcpiMcfgInfo *info)
> {
> AcpiTableMcfg *mcfg;
> - const char *sig;
> int len = sizeof(*mcfg) + 1 * sizeof(mcfg->allocation[0]);
>
> mcfg = acpi_data_push(table_data, len);
> @@ -2411,19 +2410,7 @@ build_mcfg_q35(GArray *table_data, BIOSLinker *linker,
> AcpiMcfgInfo *info)
> mcfg->allocation[0].start_bus_number = 0;
> mcfg->allocation[0].end_bus_number = PCIE_MMCFG_BUS(info->mcfg_size - 1);
>
> - /* MCFG is used for ECAM which can be enabled or disabled by guest.
> - * To avoid table size changes (which create migration issues),
> - * always create the table even if there are no allocations,
> - * but set the signature to a reserved value in this case.
> - * ACPI spec requires OSPMs to ignore such tables.
> - */
> - if (info->mcfg_base == PCIE_BASE_ADDR_UNMAPPED) {
> - /* Reserved signature: ignored by OSPM */
> - sig = "QEMU";
> - } else {
> - sig = "MCFG";
> - }
> - build_header(linker, table_data, (void *)mcfg, sig, len, 1, NULL, NULL);
> + build_header(linker, table_data, (void *)mcfg, "MCFG", len, 1, NULL,
> NULL);
> }
>
> /*
> @@ -2592,6 +2579,9 @@ static bool acpi_get_mcfg(AcpiMcfgInfo *mcfg)
> }
> mcfg->mcfg_base = qnum_get_uint(qobject_to(QNum, o));
> qobject_unref(o);
> + if (mcfg->mcfg_base == PCIE_BASE_ADDR_UNMAPPED) {
> + return false;
> + }
>
> o = object_property_get_qobject(pci_host, PCIE_HOST_MCFG_SIZE, NULL);
> assert(o);
>
Reviewed-by: Philippe Mathieu-Daudé <phi...@redhat.com>
