When booting the BSP the portion of the code executed from the trampoline page will be using the GDT located in the hypervisor .text.head section rather than the GDT located in the trampoline page.
If skip_realmode is not set the GDT located in the trampoline page will be loaded after having executed the BIOS call, otherwise the GDT from .text.head will be used for all the protected mode trampoline code execution. Note that both gdt_boot_descr and gdt_48 contain the same entries, but the former is located inside the hypervisor .text section, while the later lives in the relocated trampoline page. This is not harmful as-is, as both GDTs contain the same entries, but for consistency with the APs switch the BSP trampoline code to also use the GDT on the trampoline page. Signed-off-by: Roger Pau Monné <[email protected]> --- xen/arch/x86/boot/trampoline.S | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/xen/arch/x86/boot/trampoline.S b/xen/arch/x86/boot/trampoline.S index cdecf949b410..e4b4b9091d0c 100644 --- a/xen/arch/x86/boot/trampoline.S +++ b/xen/arch/x86/boot/trampoline.S @@ -164,6 +164,12 @@ GLOBAL(trampoline_cpu_started) .code32 trampoline_boot_cpu_entry: + /* + * Load the GDT from the relocated trampoline page rather than the + * hypervisor .text section. + */ + lgdt bootsym_rel(gdt_48, 4) + cmpb $0,bootsym_rel(skip_realmode,5) jnz .Lskip_realmode -- 2.40.0
