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Re: [Xen-devel] Re: [PATCH] switch to a known good/static GDT beforekexe
| To: | Jan Beulich <JBeulich@xxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] Re: [PATCH] switch to a known good/static GDT beforekexec |
| From: | Keir Fraser <keir.fraser@xxxxxxxxxxxxx> |
| Date: | Thu, 02 Jul 2009 13:38:08 +0100 |
| Cc: | "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx> |
| Delivery-date: | Thu, 02 Jul 2009 05:39:29 -0700 |
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| Thread-index: | Acn7CpIwZ9n09n6TQGy0FDS+0hJ09AAB2GbG |
| Thread-topic: | [Xen-devel] Re: [PATCH] switch to a known good/static GDT beforekexec |
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On 02/07/2009 12:45, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote: >>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 02.07.09 13:11 >>> >> I have one more question then -- when need_full_gdt(n), why do we always >> unconditionally rewrite the l1es mapping the reserved gdt entries? Shouldn't >> that be done on vcpu creation only and perhaps on compat mode switch (i.e., >> isn't it wasteful to do it in the context switch path)? > > While that's correct, we're talking about a single memory write here (plus > the setup code), which I think is no more wasteful than adding the extra > checking that would be needed to see whether we switch between > compat and !compat (including the !need_full_gdt(p) case, where we > don't know what kind of mapping we currently have). Hm yes, fair enough. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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