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[Qemu-devel] [PATCH v2] acpi: Use apic_id_limit when calculating legacy

From: Eduardo Habkost
Subject: [Qemu-devel] [PATCH v2] acpi: Use apic_id_limit when calculating legacy ACPI table size
Date: Fri, 11 Nov 2016 14:45:42 -0200

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 <address@hidden>
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 
         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,

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