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Re: [Xen-devel] [PATCH v2 6/6] x86/boot: Do not use trampoline for no-real-mode boot paths

On 19.08.2019 17:25, David Woodhouse wrote:
On Mon, 2019-08-12 at 12:55 +0200, Jan Beulich wrote:
On 09.08.2019 17:02, David Woodhouse wrote:
@@ -97,7 +100,7 @@ GLOBAL(trampoline_realmode_entry)
          lidt    trampsym(idt_48)
-        lgdt    trampsym(gdt_48)
+        lgdtl   trampsym(gdt_48)

Stray / unrelated change (and if needed, then also for lidt)?

The difference between 16bit l.dt and 32-bit l.dtl is that the former
only loads 24 bits of the actual table address (trampoline_gdt in this

Thus, when trampoline_gdt is being used in-place, as it is during early
boot, and *if* the Xen image is loaded higher than 16MiB, lgdt doesn't
work. That's half a day of my life I want back.

But isn't this an issue even independent of your series? I.e. doesn't
this want to be fixed in a separate (to be backported) patch?


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