Re: [PATCH v4 0/5] ARM: decompressor: use by-VA cache maintenance for v7 cores

* Ard Biesheuvel [off-list ref] [200226 16:58]:

While making changes to the EFI stub startup code, I noticed that we are
still doing set/way maintenance on the caches when booting on v7 cores.
This works today on VMs by virtue of the fact that KVM traps set/way ops
and cleans the whole address space by VA on behalf of the guest, and on
most v7 hardware, the set/way ops are in fact sufficient when only one
core is running, as there usually is no system cache. But on systems
like SynQuacer, for which 32-bit firmware is available, the current cache
maintenance only pushes the data out to the L3 system cache, where it
is not visible to the CPU once it turns the MMU and caches off.

So instead, switch to the by-VA cache maintenance that the architecture
requires for v7 and later (and ARM1176, as a side effect).

Changes since v3:
- ensure that the region that is cleaned after self-relocation of the zImage
  covers the appended DTB, if present

I gave these a try on top of the earlier "arm: fix Kbuild issue caused
by per-task stack protector GCC plugin" and booting still works for
me on armv7 including appended dtb:

Tested-by: Tony Lindgren <tony@atomide.com>

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