Hi, maintainers, I recently did some tests for this series, the benchmark is here: https://github.com/antonblanchard/will-it-scale/blob/master/tests/context_switch1.c The purpose is to check what's the overall performance impact in thread/process context- switch when CET supervisor state bit, i.e., RFBM[12], is fixed with 0 or 1 in xsaves/xrstors. 3 cases are tested: case 1: stock v6.10-rc1 kernel. case 2: v6.10-rc1 kernel + this patch series so that RFBM[12] == 0 for normal thread/process. case 3: v6.10-rc1 kernel + this patch series and with patch 3(Introduce XFEATURE_MASK_KERNEL_DYNAMIC xfeature set) reverted so that RFBM[12] == 1 for normal thread process. Run below command 10 times in each case: ./context_switch1_processes -s 20 -t 50 -n Trim the results by removing the top and down 10% of the data in each case, and I got below numbers: case 1:16444675.45Set as 1 case 2:16412285.61~99.80% case 3:16405716.19~99.76% As you can see from the results, in case 2 with optimization based on XFEATURE_MASK_KERNEL_DYNAMIC, the performance gain is ~0.2%. So I'm not sure whether XFEATURE_MASK_KERNEL_DYNAMIC and related changes are worth or not for this series. Could you share your thoughts? Thanks a lot!
