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Re: [Xen-devel] [semi-urgent Xen CS question] Re: git commit 9fd67b4ed0714ab718f1f9bd14c344af336a6df7 (x86-64: Give vvars their own page) breaks Xen PV guests (64-bit).

On 07/27/2011 09:02 AM, Andrew Lutomirski wrote:
> My current patch adds a field to pv_info.  I agree it's ugly.

Hm, that's not so bad as actually adding a new op though.

> How terrible would it be to stop using VCGF_in_syscall so we can keep
> __USER_CS?  Is there a real performance advantage to VCGF_in_syscall?

I don't know.  64-bit PV guests are already pretty horrid because of all
the pagetable switching, so it may be that iret vs sysret disappears in
the wash.  It's certainly a cleaner fix, but I would want to measure it
before committing to it.


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