[Xen-devel] Linux'es free_initmem() on Xen

["Jan Beulich" <JBeulich@xxxxxxxx>]

All,

while looking into some of the DEBUG_WX issues I came across
aforementioned function and started wondering how pv-ops gets
away without the unmapping XenoLinux has always been doing
(in free_init_pages()). Inspecting
/sys/kernel/debug/kernel_page_tables, I indeed see the area
mapped (and even r/w) in both the kernel VA range and the 1:1
mapping. While I could see page table creation code (as being
arch specific) to know of this and update both mappings when
needed (albeit I can't seem to find respective code), I don't think
the balloon driver or code exchanging pages to guarantee
address restrictions can be expected to special case this. For my
education - what am I overlooking (or is there an actual issue)?

Thanks, Jan


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