Messages in this thread | | | Date | Thu, 23 Apr 2015 15:31:49 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] x86/asm/entry/32: Restore %ss before SYSRETL if necessary |
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On 04/23/2015 03:29 PM, Andy Lutomirski wrote: >> >> Yes, the NULL SS is a special thing in 64-bit mode. I agree that >> context-switching it is probably the way to go; it should be cheap >> enough. We might even be able to conditionalize it on an X86_BUG_ flag. > > I still don't see why context switches are a better place than just > before sysret, but I could be convinced. >
Because there are way more sysrets than context switches, and Linux is particularly sensitive to system call latency, by design.
-hpa
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