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xen-ia64-devel
[Xen-ia64-devel] Re: [PATCH 04/15] ia64/pv_ops: introduce pv_info which
Dong, Eddie wrote:
Rather than making these binary patches, why not make them fast
syscalls and using a vdso page. Some of the priviledged instructions
are simply reads and we could have that information in a read-only
data page, so there is no need to do a context switch at all. Others
could benefit from a fast system call that doesn't do a full context
switch.
The issue is we don't want to change Linux code a lot, otherwise it
won't be accepted. If we use same logic with original Linux,
but it is using indirect function call now, binary patching could help
in performance.
Hi Eddie,
Sorry but this is a wrong assumption. If the code is correct then there
is no reason why it will not be accepted. It's far more important to
avoid ugly clutter that makes the code hard to maintain.
It would be nice if we could come up with a generic implementation for
such a vdso style interface that could be shared between
xen/kvm/lguest.
Introducing a new mechanism to use it to replace Linux code to use them
is another different story.
If someone starts doing a fast syscall implementation for hypercalls, it
is obvious the person(s) will be asked to make it generic on ia64.
Anything else would be silly, but it would definitely be a good thing to
do.
Cheers,
Jes
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