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

[Michael S. Tsirkin]

On Mon, Apr 23, 2018 at 11:57:04PM +0300, Michael S. Tsirkin wrote:
> 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.

In addition, isn't https://github.com/acpica/acpica/commit/0c08790c
trying to fix exactly this configuration?

> > 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 */);
> 
> 
> -- 
> MST