Messages in this thread | | | From | "Bae, Chang Seok" <> | Subject | Re: [PATCH v5 14/28] x86/fpu/xstate: Prevent unauthorised use of dynamic user state | Date | Tue, 29 Jun 2021 17:43:02 +0000 |
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On Jun 16, 2021, at 12:01, Dave Hansen <dave.hansen@intel.com> wrote: > On 6/16/21 11:47 AM, Bae, Chang Seok wrote: >> Reading XINUSE via XGETBV is cheap but not free. I don't know spending a >> hundred cycles for this WARN is big deal but this is one of the most >> performance-critical paths. > Is XGETBV(1) really a hundred cycles? That seems absurdly high for a > non-serializing register read.
My apologies -- I neglect not to check the log immediately. XGETBV(1) took about 26 cycles on my test.
Thanks, Chang
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