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Re: [Xen-devel] [PATCH v2 5/6] x86/boot: Copy 16-bit boot variables back up to Xen image

On 19.08.2019 17:25, David Woodhouse wrote:
On Mon, 2019-08-12 at 12:24 +0200, Jan Beulich wrote:
On 09.08.2019 17:02, David Woodhouse wrote:
@@ -227,7 +231,7 @@ start64:
          .word   0
  idt_48: .word   0, 0, 0 # base = limit = 0
          .word   0
-gdt_48: .word   6*8-1
+gdt_48: .word   7*8-1
          .long   tramp32sym_rel(trampoline_gdt,4)

You don't grow trampoline_gdt here, so I think this change is
wrong. And if a change was needed at all (perhaps in the next
patch), then I think it would be better to replace the use of
literal numbers, using the difference of two labels instead
(the "end" lable preferably being a .L-prefixed one).

I don't grow it but... count it ☺.

I do start using sym_fs() here in places that it wasn't before, so the
incorrect size started to *matter* because the BOOT_FS selector wasn't
included in the limit.

Oh, I see - a (latent) bug introduced by b28044226e. Should perhaps
be a separate patch to fix this then (by, as suggested, using an
"end" label rather than hard coded numbers).


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