Messages in this thread | | | Date | Mon, 23 Apr 2007 23:19:05 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: [PATCH 03/25] xen: Add nosegneg capability to the vsyscall page notes |
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Roland McGrath wrote: >> I have to admit I still don't really understand all this. Is it >> documented somewhere? >> > > I have explained it in public more than once, but I don't know off hand > anywhere that was helpfully recorded. >
Thanks very much. I'd been poking about, but the closest I came to an actual description was various patches fixing bugs, so it was a little incomplete.
> For example, a Xen-enabled kernel can use a single vDSO image (or a single > pair of int80/sysenter images), containing the "nosegneg" hwcap note. When > there is no need for it (native or hvm or 64-bit hv or whatever), it just > clears the mask word. If you actually do this, you'll want to modify the > NOTE_KERNELCAP_BEGIN macro to define a global label you can use with VDSO_SYM. >
Thanks for the pointer. I'd been getting a bit of heat for enabling the nonegseg flag unconditionally. If I can make Xen-specific then that will be one less source of complaints.
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