Re: [Xen-devel] Re: [PATCH] switch to a known good/static GDT beforekexec

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 02.07.09 13:11 >>>
>I have one more question then -- when need_full_gdt(n), why do we always
>unconditionally rewrite the l1es mapping the reserved gdt entries? Shouldn't
>that be done on vcpu creation only and perhaps on compat mode switch (i.e.,
>isn't it wasteful to do it in the context switch path)?

While that's correct, we're talking about a single memory write here (plus
the setup code), which I think is no more wasteful than adding the extra
checking that would be needed to see whether we switch between
compat and !compat (including the !need_full_gdt(p) case, where we
don't know what kind of mapping we currently have).

Jan


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