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Re: [Qemu-devel] [PATCH v2] acpi: Use apic_id_limit when calculating leg
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH v2] acpi: Use apic_id_limit when calculating legacy ACPI table size |
Date: |
Fri, 11 Nov 2016 19:13:25 +0200 |
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 <address@hidden>
Does this affect migration in some way?
> ---
> 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