Hi Dave, On 2021-12-11 at 16:02:06 +0800, Pengfei Xu wrote: > Hi Dave, > > On 2021-12-10 at 08:48:08 -0800, Dave Hansen wrote: > > On 12/9/21 8:47 PM, Pengfei Xu wrote: > > > How about the following changes: > > > Will remove set_avx2_ymm() and will only check XSAVE_MASK_FP, XSAVE_MASK_OPMASK > > > and XSAVE_MASK_PKRU xstates after signal handling and process switch, > > > > First and foremost, the whole point of these tests is to ensure that the > > kernel is properly maintaining register state. Removing registers from > > the test moves *away* from the primary goal of this test. > > > Thanks for suggestion! > Actually, I already removed any useless libc function before and after > xsave action, only left the test action between xsave action: > " > XSAVE(xsave_buf2, XSAVE_TEST_MASK); > do raise signal or fork test > XSAVE(xsave_buf3, XSAVE_TEST_MASK); > " > I found that after fork() function in virtual machine, XMM0 or XMM1 register > will be used and changed. > But in YMM xstate, I haven't see signal handline and fork action will use > and change YMM regiseters in the test. Seems we could keep YMM xstate test. > Seems it needs some other better way for XMM xstate. > > > Second, you just listed three states there. Have you considered looking > > at whether those have the same problem as the XMM/YMM registers? Please do. > > > I have tested FP, AVX512 opmask and pkru xstates on different platforms and > virtual machine, gdb these 3 xstates with fork and signal handling even printf, > above 3 functions will not use and change above 3 xstates. I used previous > xsave instruction tests to get the results. > > > Third (and I've also suggested this before), we should explicitly tell > > the compiler not to use the FPU registers. This is what the kernel > > does, and it's what allows us to, for instance, make function calls in > > the kernel without clobbering userspace content in XSAVE-managed registers. > > > > If we did that, then we would only have to worry about calls to things > > *outside* of the test program, like libc. > Thanks! Yes, I will add "float a = 0.12, b = 0.34; a = a + b;" to tell > libc process, float points has been used. > Seems if there is no addition, subtraction, multiplication or division, > there is no change in FP xstate compared with no float definition. If there > is above operation, mxcsr(xstate offset 0x18-0x1b bytes)will change from 801f > to a01f. Rounding control bit change from 00 to 01. > Sorry, I misunderstood your meaning in the last email, I should directly add syscall function between the 2 xsave comparisons, it will not use XMM, YMM and so on xstates, and I could add them back. For example, for "fork", I will use syscall(SYS_fork) instead of fork(). > Thanks! > BR.
