[PATCH v2 3/3] lmb: consider EFI memory map

Thu Jan 12 02:13:02 CET 2023

On Thu, Jan 12, 2023 at 12:35:15AM +0100, Heinrich Schuchardt wrote:
> 
> 
> On 1/11/23 23:59, Mark Kettenis wrote:
> > > From: Simon Glass <sjg at chromium.org>
> > > Date: Wed, 11 Jan 2023 14:08:27 -0700
> > 
> > Hi Simon,
> > 
> > > Hi Heinrich,
> > > 
> > > On Wed, 11 Jan 2023 at 11:03, Heinrich Schuchardt
> > > <heinrich.schuchardt at canonical.com> wrote:
> > > > 
> > > > 
> > > > 
> > > > On 1/11/23 18:55, Simon Glass wrote:
> > > > > Hi Heinrich,
> > > > > 
> > > > > On Wed, 11 Jan 2023 at 09:59, Heinrich Schuchardt
> > > > > <heinrich.schuchardt at canonical.com> wrote:
> > > > > > 
> > > > > > 
> > > > > > 
> > > > > > On 1/11/23 17:48, Simon Glass wrote:
> > > > > > > Hi,
> > > > > > > 
> > > > > > > On Wed, 11 Jan 2023 at 06:59, Tom Rini <trini at konsulko.com> wrote:
> > > > > > > > 
> > > > > > > > On Wed, Jan 11, 2023 at 08:43:37AM +0100, Heinrich Schuchardt wrote:
> > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > On 1/11/23 01:15, Simon Glass wrote:
> > > > > > > > > > Hi Heinrich,
> > > > > > > > > > 
> > > > > > > > > > On Mon, 9 Jan 2023 at 13:53, Heinrich Schuchardt
> > > > > > > > > > <heinrich.schuchardt at canonical.com> wrote:
> > > > > > > > > > > 
> > > > > > > > > > > 
> > > > > > > > > > > 
> > > > > > > > > > > On 1/9/23 21:31, Simon Glass wrote:
> > > > > > > > > > > > Hi Mark,
> > > > > > > > > > > > 
> > > > > > > > > > > > On Mon, 9 Jan 2023 at 13:20, Mark Kettenis <mark.kettenis at xs4all.nl> wrote:
> > > > > > > > > > > > > 
> > > > > > > > > > > > > > From: Simon Glass <sjg at chromium.org>
> > > > > > > > > > > > > > Date: Mon, 9 Jan 2023 13:11:01 -0700
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > > Hi Heinrich,
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > > 
> > > > > > > > > > > > > > We need to fix how EFI does addresses. It seems to use them as
> > > > > > > > > > > > > > pointers but store them as u64 ?
> > > > > > > > > > > 
> > > > > > > > > > > That is similar to what you have been doing with physical addresses.
> > > > > > > > > > > 
> > > > > > > > > > > > > 
> > > > > > > > > > > > > They're defined to a 64-bit unsigned integer by the UEFI
> > > > > > > > > > > > > specification, so you can't change it.
> > > > > > > > > > > > 
> > > > > > > > > > > > I don't mean changing the spec, just changing the internal U-Boot
> > > > > > > > > > > > implementation, which is very confusing. This confusion is spreading
> > > > > > > > > > > > out, too.
> > > > > > > > > > > > 
> > > > > > > > > > > > Regards,
> > > > > > > > > > > > Simon
> > > > > > > > > > > 
> > > > > > > > > > > The real interesting thing is how memory should be managed in U-Boot:
> > > > > > > > > > > 
> > > > > > > > > > > I would prefer to create a shared global memory management on 4KiB page
> > > > > > > > > > > level used both for EFI and the rest of U-Boot.
> > > > > > > > > > 
> > > > > > > > > > Sounds good.
> > > > > > > > > > 
> > > > > > > > > > > 
> > > > > > > > > > > What EFI adds to the requirements is that you need more than free
> > > > > > > > > > > (EfiConventionalMemory) and used memory. EFI knows 16 different types of
> > > > > > > > > > > memory usage (see enum efi_memory_type).
> > > > > > > > > > 
> > > > > > > > > > That's a shame. How much of this is legacy and how much is useful?
> > > > > > > > > > 
> > > > > > > > > > > 
> > > > > > > > > > > When loading a file (e.g. with the "load" command) this should lead to a
> > > > > > > > > > > memory reservation. You should not be able to load a second file into an
> > > > > > > > > > > overlapping memory area without releasing the allocated memory first.
> > > > > > > > > > > 
> > > > > > > > > > > This would replace lmb which currently tries to recalculate available
> > > > > > > > > > > memory ab initio again and again.
> > > > > > > > > > > 
> > > > > > > > > > > With managed memory we should be able to get rid of all those constants
> > > > > > > > > > > like $loadaddr, $fdt_addr_r, $kernel_addr_r, etc. and instead use a
> > > > > > > > > > > register of named loaded files.
> > > > > > > > > > 
> > > > > > > > > > This is where standard boot comes in, since it knows what it has
> > > > > > > > > > loaded and has pointers to it.
> > > > > > > > > > 
> > > > > > > > > > I see a future where we don't use these commands when we want to save
> > > > > > > > > > space. It can save 300KB from the U-Boot size.
> > > > > > > > > > 
> > > > > > > > > > But this really has to come later, since there is so much churn already!
> > > > > > > > > > 
> > > > > > > > > > For now, please don't add EFI allocation into lmb..that is just odd.
> > > > > > > > > 
> > > > > > > > > It is not odd but necessary. Without it the Odroid C2 does not boot but
> > > > > > > > > crashes.
> > > > > > > > 
> > > > > > > > It's not Odroid C2, it's anything that with the bad luck to relocate
> > > > > > > > over the unprotected EFI structures.
> > > > > > > 
> > > > > > > So can EFI use the lmb calls to reserve its memory? This patch is backwards.
> > > > > > 
> > > > > > Simon, the EFI code can manage memory, LMB cannot.
> > > > > > 
> > > > > > Every time something in U-Boot invokes LMB it recalculates reservations
> > > > > > *ab initio*.
> > > > > > 
> > > > > > You could use lib/efi_loader/efi_memory to replace LMB but not the other
> > > > > > way round.
> > > > > > 
> > > > > > We should discard LMB and replace it by proper memory management.
> > > > > 
> > > > > We have malloc() but in general this is not used (so far) except with
> > > > > some parts of standard boot, and even there we are maintaining
> > > > > compatibility with existing fdt_addr_r vars, etc.
> > > > 
> > > > malloc() currently manages a portion of the memory defined by
> > > > CONFIG_SYS_MALLOC_LEN. It cannot manage reserved memory. I don't know if
> > > > it can allocate from non-consecutive memory areas.
> > > 
> > > This depends on whether we do what you were talking about above, i.e.
> > > get rid of the env vars and allocate things. One way to allocate would
> > > be with malloc().
> > 
> > Almost certainly not a good idea.  There are all sorts of constraints
> > an things like the address where you load your kernel.  Something
> > like: "128M of memory, 2MB aligned not crossing a 1GB boundary".
> > 
> > Now *I* would argue that encoding the specific requirements of an OS
> > into U-Boot is the wrong approach to start with and that you're better
> > off having U-Boot load an OS-specific 2nd (or 3rd or 4th) stage loader
> > that loads the actual OS kernel.  Which is why providing an interface
> > like EFI that provides a lot of control over memory allocation is so
> > useful.
> 
> These 2nd stage boot loader are the EFI stubs of the different operating
> systems.
> 
> The non-EFI boot commands are used to call Linux' legacy entry point. We
> will have to manage the architecture specific rules in U-Boot. This requires
> a memory allocator to which we can pass an upper address and an alignment
> requirement.

Or we just say that $range is available for at-will usage. So yes, a
design document, that states the goals of what we're trying to do here,
is really the next step.

-- 
Tom
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