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xen-devel
Re: [Xen-devel] [patch 17/44] Add nosegneg capability to the vsyscall pa
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To: |
Rusty Russell <rusty@xxxxxxxxxxxxxxx> |
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Subject: |
Re: [Xen-devel] [patch 17/44] Add nosegneg capability to the vsyscall page notes |
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From: |
Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
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Date: |
Mon, 16 Jul 2007 18:04:54 -0700 |
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Cc: |
Zachary Amsden <zach@xxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>, lkml <linux-kernel@xxxxxxxxxxxxxxx>, Andi Kleen <ak@xxxxxxx>, Chris Wright <chrisw@xxxxxxxxxxxx>, Ian Pratt <ian.pratt@xxxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Ulrich Drepper <drepper@xxxxxxxxxx>, Roland McGrath <roland@xxxxxxxxxx>, Christian Limpach <Christian.Limpach@xxxxxxxxxxxx> |
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Mon, 16 Jul 2007 18:03:34 -0700 |
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Rusty Russell wrote:
> On Mon, 2007-07-16 at 16:15 -0700, Jeremy Fitzhardinge wrote:
>
>> plain text document attachment (xen-vsyscall-note.patch)
>> Add the "nosegneg" fake capabilty to the vsyscall page notes. This is
>> used by the runtime linker to select a glibc version which then
>> disables negative-offset accesses to the thread-local segment via
>> %gs. These accesses require emulation in Xen (because segments are
>> truncated to protect the hypervisor address space) and avoiding them
>> provides a measurable performance boost.
>>
>
> Hmm, this is still unconditional? Not that it causes any measurable
> slowdown when enabled, but ISTR discussing making this dynamic...
Played with it for a bit, but it's fairly fiddly. Didn't seem like it
was worth the complexity.
J
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- Re: [Xen-devel] [patch 03/44] usermodehelper: split setup from execution, (continued)
- [Xen-devel] [patch 10/44] paravirt: unstatic leave_mm, Jeremy Fitzhardinge
- [Xen-devel] [patch 12/44] paravirt: make siblingmap functions visible, Jeremy Fitzhardinge
- [Xen-devel] [patch 08/44] paravirt: add a hook for once the allocator is ready, Jeremy Fitzhardinge
- [Xen-devel] [patch 05/44] usermodehelper: Tidy up waiting, Jeremy Fitzhardinge
- [Xen-devel] [patch 06/44] use elfnote.h to generate vsyscall notes., Jeremy Fitzhardinge
- [Xen-devel] [patch 13/44] paravirt: export __supported_pte_mask, Jeremy Fitzhardinge
- [Xen-devel] [patch 17/44] Add nosegneg capability to the vsyscall page notes, Jeremy Fitzhardinge
- [Xen-devel] [patch 14/44] Allocate and free vmalloc areas, Jeremy Fitzhardinge
- [Xen-devel] [patch 23/44] xen: configuration, Jeremy Fitzhardinge
- [Xen-devel] [patch 26/44] xen: ignore RW mapping of RO pages in pagetable_init, Jeremy Fitzhardinge
- [Xen-devel] [patch 22/44] xen: time implementation, Jeremy Fitzhardinge
- [Xen-devel] [patch 33/44] xen: use the hvc console infrastructure for Xen console, Jeremy Fitzhardinge
- [Xen-devel] [patch 24/44] xen: add pinned page flag, Jeremy Fitzhardinge
- [Xen-devel] [patch 25/44] xen: Complete pagetable pinning, Jeremy Fitzhardinge
- [Xen-devel] [patch 21/44] xen: event channels, Jeremy Fitzhardinge
- [Xen-devel] [patch 38/44] xen: machine operations, Jeremy Fitzhardinge
- [Xen-devel] [patch 29/44] xen: SMP guest support, Jeremy Fitzhardinge
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