RE: [PATCH v6 5/8] acpi: Align the size to 128k

[miaoyubo <miaoyubo@huawei.com>]

> -----Original Message-----
> From: Michael S. Tsirkin [mailto:mst@redhat.com]
> Sent: Monday, May 4, 2020 10:03 PM
> To: miaoyubo <miaoyubo@huawei.com>
> Cc: peter.maydell@linaro.org; shannon.zhaosl@gmail.com;
> lersek@redhat.com; imammedo@redhat.com; qemu-devel@nongnu.org;
> berrange@redhat.com; Xiexiangyou <xiexiangyou@huawei.com>
> Subject: Re: [PATCH v6 5/8] acpi: Align the size to 128k
> 
> On Wed, Apr 08, 2020 at 08:58:13PM +0800, Yubo Miao wrote:
> > From: miaoyubo <miaoyubo@huawei.com>
> >
> > If table size is changed between virt_acpi_build and
> > virt_acpi_build_update, the table size would not be updated to UEFI,
> > therefore, just align the size to 128kb, which is enough and same with
> > x86. It would warn if 64k is not enough and the align size should be
> > updated.
> >
> > Signed-off-by: miaoyubo <miaoyubo@huawei.com>
> 
> does this affect migration in any way?
> 

No, it would not affect migration.
I migrated one vm between two qemus(one with tables aligned to 128k and one not)
and the vm could be migrated. 

> > ---
> >  hw/arm/virt-acpi-build.c | 25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> >
> > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c index
> > 7bcd04dfb7..89bb768b0c 100644
> > --- a/hw/arm/virt-acpi-build.c
> > +++ b/hw/arm/virt-acpi-build.c
> > @@ -54,6 +54,8 @@
> >  #include "hw/pci/pci_bridge.h"
> >  #define ARM_SPI_BASE 32
> >
> > +#define ACPI_BUILD_TABLE_SIZE             0x20000
> > +
> >  static void acpi_dsdt_add_cpus(Aml *scope, int smp_cpus)  {
> >      uint16_t i;
> > @@ -883,6 +885,15 @@ struct AcpiBuildState {
> >      bool patched;
> >  } AcpiBuildState;
> >
> > +static void acpi_align_size(GArray *blob, unsigned align) {
> > +    /*
> > +     * Align size to multiple of given size. This reduces the chance
> > +     * we need to change size in the future (breaking cross version
> migration).
> > +     */
> > 2.19.1
> >

Regards,
Miao