Re: [Qemu-devel] RFC: altering the NVDIMM acpi table

[Michael S. Tsirkin]

On Mon, Apr 23, 2018 at 08:35:45PM +0000, Schmauss, Erik wrote:
> Hello,
> 
> I work on ACPICA and we have recently made changes to the behavior of 
> the Linux AML interpreter to match other OS implementations. After 
> sending the patches to upstream Linux, we have identified that 
> hw/acpi/nvdimm.c specifies an ACPI table with a forward reference
>  (MEMA is a forward reference that is no longer supported as of Linux 
> 4.17-rc1).

Interesting. What is the result if such a table is encountered?
Will this break on old hypervisors that already
shipped with this set of tables?

> We would like to change this file to move the declaration of Name 
> (MEMA,...) to appear as the very first declaration in the SSDT. Below is a 
> patch outlining the change that I would like to make. 

I think this will work just fine, but I would like to see a
comment explaining what the issue is.
Names aren't actually resolved until method actually runs, right?
For example, a name could be defined by a dynamically loaded
definition block ...

> However, I am having a hard time getting make check to run
>  to completion in a reasonable amount of time. It always seems to fail 
> on some sort of checksum test...

Are you running this on Linux? On bare metal or within a VM?
Most people here test it on Linux with KVM.

> It would be great if you could let me 
> know what you think of the change and what I can do to speed up the 
> execution time of make check...

You could limit to just qtest tests.

make check-qtest

> 
> Thanks,
> 
> Erik Schmauss
> 
> diff --git a/hw/acpi/nvdimm.c b/hw/acpi/nvdimm.c
> index 59d6e4254c..7c9efd9ac7 100644
> --- a/hw/acpi/nvdimm.c
> +++ b/hw/acpi/nvdimm.c
> @@ -1234,6 +1234,9 @@ static void nvdimm_build_ssdt(GArray *table_offsets, 
> GArray *table_data,
>      ssdt = init_aml_allocator();
>      acpi_data_push(ssdt->buf, sizeof(AcpiTableHeader));
>  
> +    mem_addr_offset = build_append_named_dword(table_data,
> +                                               NVDIMM_ACPI_MEM_ADDR);
> +
>      sb_scope = aml_scope("\\_SB");
>  
>      dev = aml_device("NVDR");
> @@ -1266,9 +1269,6 @@ static void nvdimm_build_ssdt(GArray *table_offsets, 
> GArray *table_data,
>  
>      /* copy AML table into ACPI tables blob and patch header there */
>      g_array_append_vals(table_data, ssdt->buf->data, ssdt->buf->len);
> -    mem_addr_offset = build_append_named_dword(table_data,
> -                                               NVDIMM_ACPI_MEM_ADDR);
> -
>      bios_linker_loader_alloc(linker,
>                               NVDIMM_DSM_MEM_FILE, dsm_dma_arrea,
>                               sizeof(NvdimmDsmIn), false /* high memory */);


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MST