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Re: [Xen-devel] [PATCH] add canonical address checks to HVM
| To: | "Keir Fraser" <keir@xxxxxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] [PATCH] add canonical address checks to HVM |
| From: | "Jan Beulich" <jbeulich@xxxxxxxxxx> |
| Date: | Fri, 01 Dec 2006 11:10:04 +0000 |
| Cc: | xen-devel@xxxxxxxxxxxxxxxxxxx |
| Delivery-date: | Fri, 01 Dec 2006 03:09:33 -0800 |
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| In-reply-to: | <C195B07C.55A6%keir@xxxxxxxxxxxxx> |
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>>> Keir Fraser <keir@xxxxxxxxxxxxx> 01.12.06 11:12 >>> >On 29/11/06 15:05, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote: > >> +#ifdef __x86_64__ >> +#define IS_CANO_ADDRESS(add) (((long)(add) >> 47) == ((long)(add) >> 63)) >> +#else >> +#define IS_CANO_ADDRESS(add) 1 >> +#endif >> + > >Is there any guarantee that right-shift is signed when using gcc? I suppose so, I believe this is assumed to be that way in various other places. However, I'm not sure I have an idea where I could look up implementation defined behavior for gcc. >How about (int16_t)((add) >> 48) == -(int)(((add) >> 47) & 1) ?? Sure, should work too, but would incur more overhead. I was actually trying to even avoid the two shifts, but I wasn't able to find something that would use just one *and* would be faster than the version I submitted. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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