Hi Ilias,
On Thu, 26 Sept 2024 at 13:26, Ilias Apalodimas
<ilias.apalodi...@linaro.org> wrote:
>
> Hi Simon,
>
> On Fri, 20 Sept 2024 at 19:01, Simon Glass <s...@chromium.org> wrote:
> >
> > Hi Ilias,
> >
> > On Fri, 20 Sept 2024 at 08:36, Ilias Apalodimas
> > <ilias.apalodi...@linaro.org> wrote:
> > >
> > > Hi Simon,
> > >
> > > On Thu, 19 Sept 2024 at 18:36, Simon Glass <s...@chromium.org> wrote:
> > > >
> > > > Hi Ilias,
> > > >
> > > > On Thu, 19 Sept 2024 at 17:20, Ilias Apalodimas
> > > > <ilias.apalodi...@linaro.org> wrote:
> > > > >
> > > > > Hi Simon,
> > > > >
> > > > > On Thu, 19 Sept 2024 at 18:00, Simon Glass <s...@chromium.org> wrote:
> > > > > >
> > > > > > Hi Ilias,
> > > > > >
> > > > >
> > > > > [...]
> > > > >
> > > > > > > > > +
> > > > > > > > > + if (!addr)
> > > > > > > > > + return log_msg_ret("mem", -ENOMEM);
> > > > > > > > > + } else {
> > > > > > > > > + pages = efi_size_in_pages(TABLE_SIZE);
> > > > > > > > > +
> > > > > > > > > + ret =
> > > > > > > > > efi_allocate_pages(EFI_ALLOCATE_ANY_PAGES,
> > > > > > > > > +
> > > > > > > > > EFI_ACPI_RECLAIM_MEMORY,
> > > > > > > > > + pages,
> > > > > > > > > &new_acpi_addr);
> > > > > > > > > + if (ret != EFI_SUCCESS)
> > > > > > > > > + return log_msg_ret("mem", -ENOMEM);
> > > > > > > > > +
> > > > > > > > > + addr = (void *)(uintptr_t)new_acpi_addr;
> > > > > > > > > + }
> > > > > > > > > +
> > > > > > > >
> > > > > > > > The tables should be written regardless of whether EFI_LOADER
> > > > > > > > is enabled.
> > > > > > >
> > > > > > > *Why*? How do you expect to hand them over to the OS?
> > > > > >
> > > > > > Why - because boards which need ACPI tables to boot should generate
> > > > > > them;
> > > > >
> > > > > Noone argued that.
> > > > >
> > > > > > also this happens when U-Boot starts up, in last_stage_init()
> > > > > > How - it isn't possible, but eventually I suppose it will be, once
> > > > > > we
> > > > > > have a use case for booting with ACPI but without EFI
> > > > >
> > > > > Are you aware of such an OS? If not, we can accept the patches when we
> > > > > have a reason.
> > > >
> > > > Which patches? This is how it works today. We set up the tables in
> > > > last_stage_init(), so they can be examined while in U-Boot.
> > >
> > > What I mean, is that until we have a valid use case to store the ACPI
> > > in a bloblist, I prefer them being allocated with proper EFI memory
> > > backing
> >
> > I'm going to assert prior art here. If ARM is to have ACPI in U-Boot,
> > it should follow the most recent x86 approach and store it in the
> > bloblist. That is what the blloblist is for. It also avoids using
> > memory below the U-Boot area, which is not allowed.
>
> By prior art you mean [0], which was none of the EFI maintainers got involved?
Yes. I should point out that I wrote the original EFI app support and
am maintainer for that. I also reviewed the original EFI_LOADER
support over quite a few revisions. I have a pretty-good understanding
of the implementation and issues.
>
> >
> > >
> > > >
> > > > It is the patches to change this which I object to.
> > > >
> > > > > I remember patches being hard NAK'ed on using DTs to pass the ACPI
> > > > > table address in the past.
> > > >
> > > > Yes, I believe Bytedance carries a patch locally for that :-)
> > >
> > > Exactly
> > >
> > > >
> > > > >
> > > > > >
> > > > > > >
> > > > > > > >
> > > > > > > > Can we drop this else clause? We should always use the bloblist.
> > > > > > >
> > > > > > > Both Heinrich and I said the exact opposite. Unless there's a
> > > > > > > perfectly good reason why we should keep them in bloblist memory,
> > > > > > > I'd
> > > > > > > like us to do that
> > > > > >
> > > > > > The main reason is that we should not be putting things in memory
> > > > > > between the start of RAM and the bottom of the U-Boot area. That
> > > > > > region of memory is supposed to be for loading images. Most boards
> > > > > > hard-code the image-load addresses in environment variables. But
> > > > > > even
> > > > > > if they didn't, we should not be using that memory for U-Boot data.
> > > > >
> > > > > EFI allows you to request a specific address to use. We can choose one
> > > > > that fits the requirements
> > > >
> > > > So long as it is in U-Boot's space, that is fine. I just sent a patch
> > > > about relocation which covers this. It occured to me that this feature
> > > > of U-Boot, which I have always assumed was common knowledge, may have
> > > > not been noticed.
> > > >
> > > > > >
> > > > > > Another reason is that the bloblist is designed for this, for
> > > > > > keeping
> > > > > > tables in a small, contiguous area of memory, so that when passed to
> > > > > > Linux they are not spread all over the place.
> > > > >
> > > > > Linux does not and will not read tables from a bloblist though
> > > >
> > > > Indeed. There really isn't any point, anyway, since there are other
> > > > ways of passing the tables along...except for ACPI with FDT but that
> > > > isn't a valid use case for Linux so far.
> > >
> > > What we are trying to do with EFI is to stay as close to the spec and
> > > the current OS implementations as possible. So again, please allocate
> > > EFI memory for the ACPI tables. The patches to convert it to bloblist
> > > allocating them are minimal, so we can do it, once there's an actuall
> > > need for it.
> >
> > As it stands today, efi_acpi_register() does not do an EFI allocation,
> > it just adds the existing allocation to the EFI tables. This works
> > fine for x86 - see arch/x86/lib/tables.c -
>
> Yes and I've already mentioned that in my original response.
OK good.
>
> > so I would like ARM to do
> > the same. The need for it is (as above) that we should ensure that
> > memory usage is within the U-Boot area. This is something which
> > bloblist handles automatically. It is also nice to see all the tables
> > in one place with 'bloblist list'
>
> Unless bloblist is not compiled.... in which case you still need to
> malloc and align.
For Arm, ACPI depends on BLOBLIST. It is also required on recent x86 platforms.
> I am just putting this out there, because your next email is going to
> be "oh look bloblist is mandatory now".
> For the last time, bloblist make zero sense to allocate data that
> arent going to be handed across loaders.
Sorry, I don't agree. It makes a lot of sense, since it keeps the
tables together, and keeps them within the memory space that U-Boot
uses for itself.
I have suggested we arrange a meeting to discuss this and I am still
happy to do so.
>
> Patrick, my suggestion is to either use efi_allocate_pages() as you do
> or malloc a properly aligned buffer since we set the memory type in
> efi_acpi_register().
I don't expect to change my mind on this. The efi_allocate_pages()
call should not be used before the app starts. That is the error which
has laid latent for years without anyone knowing. I still haven't seen
a clear acknowledgement of a problem, from the EFI folks. This is not
just about images and lmb, it is about following U-Boot's memory
practices.
> IIRC the reason we set that in efi_acpi_register() is for QEMU which
> hands us over ACPI tables, so we can't do much. I would personally
> prefer efi allocated memory.
It is used on x86 as well, e.g. chromebook_coral. Also QEMU tables are
munged somewhat during the copy, so I believe we can place them where
we wish. That probably needs a clean-up too. Bear in mind though, that
the tables are sometimes placed at f0000 on x86, i.e. below any memory
used by U-Boot itself.
Regards,
Simon
