[PATCH v2] smbios: arm64: Allow table to be written at a fixed addr

[Tom Rini]

On Fri, Nov 03, 2023 at 11:12:40AM -0600, Simon Glass wrote:
> Hi,
> 
> On Sat, 28 Oct 2023 at 12:41, Simon Glass <sjg at chromium.org> wrote:
> >
> > [unfortunately I am not receiving email from the list at present]
> >
> > Hi Heinrich,
> >
> > On Wed, 25 Oct 2023 at 21:39, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
> > >
> > > On 10/25/23 04:49, Simon Glass wrote:
> > > > Hi Heinrich,
> > > >
> > > > On Tue, 24 Oct 2023 at 18:22, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
> > > >>
> > > >>
> > > >>
> > > >> Am 25. Oktober 2023 01:31:19 MESZ schrieb Simon Glass <sjg at chromium.org>:
> > > >>> U-Boot typically sets up its malloc() pool near the top of memory. On
> > > >>> ARM64 systems this can result in an SMBIOS table above 4GB which is
> > > >>> not supported by SMBIOSv2.
> > > >>>
> > > >>> Work around this problem by providing a new option to choose an address
> > > >>> below 4GB (but as high as possible), if needed.
> > > >>
> > > >> You must not overwrite memory controlled by the EFI subsystem without calling its allocator.  We should provide SMBIOS 3. SMBIOS 2 is only a fallback for outdated tools.
> > > >
> > > > That is not my intention and I don't believe this code does that. EFI
> > > > is not running at this point, is it?
> > >
> > > The function install_smbios_table() only exists if CONFIG_EFI_LOADER=y.
> >
> > That is because ARM devices don't normally need it, right? Anyway,
> > that option isn't related to this patch. If ARM devices started using
> > SMBIOS and had another way to pass it to Linux (other than EFI) then
> > we would want to install it.
> >
> > >
> > > We have:
> > > EVENT_SPY_SIMPLE(EVT_LAST_STAGE_INIT, install_smbios_table);
> > > This is invoked after efi_memory_init().
> > >
> > > The EFI specification requires that the memory area occupied by the
> > > SMBIOS table uses one of a specific set of memory types where
> > > EfiRuntimeServicesData is recommended. So you must call
> > >
> > > u64 addr = UINT_MAX;
> > > ret = efi_allocate_pages(EFI_ALLOCATE_MAX_ADDRESS,
> > > EFI_RUNTIME_SERVICES_DATA, efi_size_in_pages(size), *addr);
> > >
> > > to allocate the memory. If the return code is not EFI_SUCCESS, no memory
> > > below 4 GiB is available.
> >
> > The root problem here is that x86 and ARM used to work differently.
> > When the ARM SMBIOS stuff was done, it worked by writing the SMBIOS
> > table as part of the 'bootefi' command. On x86, the tables were
> > written on startup, so you can examine them within U-Boot. Clearly the
> > x86 approach is correct. For one thing, a previous-stage bootloader
> > may set up the tables, so it simply isn't valid to write them in that
> > case. So we need to separate writing the tables from telling EFI about
> > them.
> >
> > So I have fixed that, so ARM now writes the tables at the start. But
> > using an EFI allocation function is clearly not right. This is generic
> > code, nothing to do with EFI, really. In fact, the SMBIOS writing
> > should move out of efi_loader. The install_smbios_table() function
> > should be somewhere in lib, i suppose, with just efi_smbios_register()
> > sitting in lib/efi_loader
> >
> > Also, why is efi_memory_init() called early in init? Is there anything
> > that needs that in the init sequence? Could we move it to the end, or
> > perhaps skip it completely until the 'bootefi' command is used?
> >
> > Another point I should make is that it should be fine for U-Boot to
> > put something in memory and then call efi_add_memory_map() to tell EFI
> > about it. What problems does that cause? It isn't as if EFI allocates
> > things in the 'conventional' memory (is that the name for memory below
> > 4GB?) This is how efi_acpi_register() works.
> >
> > (Aside: it is bizarre to me that CONFIG_EFI_LOADER appears in
> > drivers/video/rockchip_rk_vop.c and other such files)
> >
> > >
> > > >
> > > > The bit I am confused about is that we don't support SMBIOS3 in
> > > > U-Boot. I am trying to fix an introduced bug...
> > >
> > > I would not know why we should not use SMBIOS 3.
> >
> > Neither do I. Perhaps there are compatibility concerns? If it is OK to
> > do that then we could go back to my previous series [1]. What do you
> > think?
> 
> Tom responded but I missed it. In part it says:
> 
> "So, can we please start by just doing the minimal changes to get the
> SMBIOS table done correctly for memory above 4G, via EFI, and then start
> the next steps?"
> 
> I am OK to do an EFI hack for ARM so long as we agree that after the
> release we will revert it and generate the table using generic memory
> allocation, not dependent on EFI. Does that sound reasonable?
> 
> I don't seem to have received any response from Heinrich to the
> various points I made above. I cannot see any response on patchwork
> either.

Drop it right after the release? No. We will replace it with what's more
appropriate once we figure out what that is. And please don't call it a
hack, unless I'm missing something I don't see yet how to make use of
the SMBIOS table on ARM without EFI.  I see something that implies MIPS
can (and loongarch and ia64).

-- 
Tom
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