[edk2-devel] [PATCH v3 resend 07/11] ArmVirtPkg/ArmVirtQemu: enable initial ID map at early boot

[Gerd Hoffmann]

On Wed, Oct 19, 2022 at 11:22:07AM +0200, Ard Biesheuvel wrote:
> Now that we have all the pieces in place, switch the AArch64 version of
> ArmVirtQemu to a mode where the first thing it does out of reset is
> enable a preliminary ID map that covers the NOR flash and sufficient
> DRAM to create the UEFI page tables as usual.
> 
> The advantage of this is that no manipulation of memory occurs any
> longer before the MMU is enabled, which removes the need for explicit
> coherency management, which is cumbersome and bad for performance.
> 
> It also means we no longer need to build all components that may execute
> with the MMU off (including BASE libraries) with strict alignment.

raspberry pi 3 host stopped working with this.  No log messages,
probably fails before enabling the serial console (not surprising
given the nature of the change).

raspberry pi 4 host continues to work fine.


Possibly related: raspberry pi 3 host (before this commit) waits forever
for a key press instead of continuing after 5 seconds timeout.  That one
is reproducible on raspberry pi 4 host using ...

	qemu-system-aarch64 -machine virt,kernel-irqchip=off

... which is default on rpi3 due to lack of a gic.  Which hints some
problem with timer interrupt (possibly a qemu bug not a edk2 armvirt
issue).

(not that much of a problem in practice given that the rpi3 isn't a
great platform with only 1G of ram, but due to supply chain problems
it is hard to get your hands on a rpi4 right now so I'm trying to use
the rpi3 I have lying around ...).

take care,
  Gerd



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