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Date: Wed, 30 Jul 2014 17:25:25 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2] Add ACPI tables for TPM
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To: Stefan Berger <stefanb@us.ibm.com>
Cc: lersek@redhat.com, qemu-devel@nongnu.org, Stefan Berger <stefanb@linux.vnet.ibm.com>

On Wed, Jul 30, 2014 at 11:13:07AM -0400, Stefan Berger wrote:
> "Michael S. Tsirkin" <mst@redhat.com> wrote on 07/30/2014 11:07:28 AM:
> 
> 
> > > >If you need bios to allocate this memory, then we will
> > > >need a new allocation type for this, add it to linker
> > > >in bios and qemu.
> > >
> > > Why does the BIOS 'need' to allocate it? Why can it not just use the memory
> > > that QEMU allocates? Obviously I am using the 'pointer relocation' feature
> > > of the BIOS to bend the pointer in the TCPA table to this log area.
> >
> > You tell me - your patches make BIOS allocate it.
> 
> No, the BIOS does not allocate it, it merely relocates the pointer.

Yes it does :)
You pushed the log as part of the table_data which bios
allocates memory for, and reads from QEMU.

> One example here:
> 
>     fadt->firmware_ctrl = cpu_to_le32(facs);
>     /* FACS address to be filled by Guest linker */
>     bios_linker_loader_add_pointer(linker, ACPI_BUILD_TABLE_FILE,  
>                                    ACPI_BUILD_TABLE_FILE,
>                                    table_data, &fadt->firmware_ctrl,
>                                    sizeof fadt->firmware_ctrl);
> 
> similar example here:
> 
>     log_area_start_address = table_data->len + sizeof(*tcpa);
>  
>     [...]
>     tcpa->log_area_start_address = cpu_to_le64(log_area_start_address);
> 
>     /* LASA address to be filled by Guest linker */
>     bios_linker_loader_add_pointer(linker, ACPI_BUILD_TABLE_FILE,
>                                    ACPI_BUILD_TABLE_FILE,
>                                    table_data, &tcpa->log_area_start_address,
>                                    sizeof(tcpa->log_area_start_address));
> 
> 
> 
>    Stefan


It relocates it to within the table that it allocated.