On Fri, Nov 11, 2016 at 07:13:25PM +0200, Michael S. Tsirkin wrote: > On Fri, Nov 11, 2016 at 02:45:42PM -0200, Eduardo Habkost wrote: > > The code that calculates the legacy ACPI table size for migration > > compatibility uses max_cpus when calculating legacy_aml_len (the size of > > the DSDT and SSDT tables). However, the SSDT grows according to APIC ID > > limit, not max_cpus. > > > > The bug is not triggered very often because of the 4k alignment on the > > table size. But it can be triggered if you are unlucky enough to cross a > > 4k boundary. > > > > Change the legacy_aml_len calculation to use apic_id_limit, to calculate > > the right size. > > > > Signed-off-by: Eduardo Habkost <ehabk...@redhat.com> > > Does this affect migration in some way?
It affects migration in the same way that a wrong PCMachineClass::legacy_acpi_table_size value would. (I don't know what are the exact symptoms when the sizes are wrong) In 2014 I could even trigger the "Warning: migration may not work." message before applying this fix, I think it was because the difference between aml_len and legacy_aml_len was smaller. But something changed in between and the effects of the wrong size calculation are harder to see. > > > --- > > This patch was submitted in 2014 and reviewed by Paolo. Only > > today I noticed that it was never merged. > > > > Changes v1 -> v2: > > * Use pcms->apic_id_limit, as guest_info doesn't exist anymore > > --- > > 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 c02f408..bb66446 100644 > > --- a/hw/i386/acpi-build.c > > +++ b/hw/i386/acpi-build.c > > @@ -2859,7 +2859,7 @@ void acpi_build(AcpiBuildTables *tables, MachineState > > *machine) > > */ > > int legacy_aml_len = > > pcmc->legacy_acpi_table_size + > > - ACPI_BUILD_LEGACY_CPU_AML_SIZE * max_cpus; > > + ACPI_BUILD_LEGACY_CPU_AML_SIZE * pcms->apic_id_limit; > > int legacy_table_size = > > ROUND_UP(tables_blob->len - aml_len + legacy_aml_len, > > ACPI_BUILD_ALIGN_SIZE); > > -- > > 2.7.4 -- Eduardo
