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Re: [Xen-devel] [PATCH v3 07/32] xen/x86: fix arch_set_info_guest for HVM guests

El 05/08/15 a les 17.39, Andrew Cooper ha escrit:
> On 05/08/15 10:53, Roger Pau Monné wrote:
>> El 04/08/15 a les 20.08, Andrew Cooper ha escrit:
>>> On 03/08/15 18:31, Roger Pau Monné wrote:
>>>>     uint32_t cs_base;
>>>>     uint32_t ds_base;
>>>>     uint32_t ss_base;
>>>>     uint32_t cs_limit;
>>>>     uint32_t ds_limit;
>>>>     uint32_t ss_limit;
>>>>     uint16_t cs_ar;
>>>>     uint16_t ds_ar;
>>>>     uint16_t ss_ar;
>>> You need selector entries for each segment as well.
>> Really? What's the point in having the selector if we don't have a GDT,
>> and we allow loading the cached part, which is the relevant one.
> push %cs; push 1f; lret
> At all points when segment details are updated, it is the responsibility
> of software to ensure that the details match with the GDT/LDT entry. 
> See for example the Intel and AMD manuals for syscall/sysenter where
> similar "updating segment details behind the scenes" occurs.

I would certainly expect the user to have loaded a proper GDT and
reloaded the segments selectors before attempting to do something like
the above.

I really don't mind adding a cs_sel, ds_sel, ss_sel and tr_sel, I just
think it's quite pointless because it's common practice to load a GDT
and then reload the segment selectors to point to the right entries.


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