Hi Dave,
On Tue, Nov 9, 2021 at 1:49 AM Dave Hansen dave.hansen@intel.com wrote:
Well, gosh, it's making it back to the software init value. If you do:
echo 0x15555554 > /sys/kernel/debug/x86/init_pkrudo you end up with 0x15555554 as the value?
What's interesting is that writing to init_pkru fails with -EINVAL for me, and I've traced it down to get_xsave_addr() returning NULL on the following check:
/* * This assumes the last 'xsave*' instruction to * have requested that 'xfeature_nr' be saved. * If it did not, we might be seeing and old value * of the field in the buffer. * * This can happen because the last 'xsave' did not * request that this feature be saved (unlikely) * or because the "init optimization" caused it * to not be saved. */ if (!(xsave->header.xfeatures & BIT_ULL(xfeature_nr))) return NULL;
And that's why I thought this was possibly related to that erratum that I shared before.
Does your system have any more XSAVE support than mine?
kernel: [ 0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers' kernel: [ 0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers' kernel: [ 0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers' kernel: [ 0.000000] x86/fpu: Supporting XSAVE feature 0x020: 'AVX-512 opmask' kernel: [ 0.000000] x86/fpu: Supporting XSAVE feature 0x040: 'AVX-512 Hi256' kernel: [ 0.000000] x86/fpu: Supporting XSAVE feature 0x080: 'AVX-512 ZMM_Hi256' kernel: [ 0.000000] x86/fpu: Supporting XSAVE feature 0x200: 'Protection Keys User registers' kernel: [ 0.000000] x86/fpu: xstate_offset[2]: 576, xstate_sizes[2]: 256 kernel: [ 0.000000] x86/fpu: xstate_offset[5]: 832, xstate_sizes[5]: 64 kernel: [ 0.000000] x86/fpu: xstate_offset[6]: 896, xstate_sizes[6]: 512 kernel: [ 0.000000] x86/fpu: xstate_offset[7]: 1408, xstate_sizes[7]: 1024 kernel: [ 0.000000] x86/fpu: xstate_offset[9]: 2432, xstate_sizes[9]: 8 kernel: [ 0.000000] x86/fpu: Enabled xstate features 0x2e7, context size is 2440 bytes, using 'compacted' format.
No, it's pretty much identical
INFO kernel: [ 0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers' INFO kernel: [ 0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers' INFO kernel: [ 0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers' INFO kernel: [ 0.000000] x86/fpu: Supporting XSAVE feature 0x020: 'AVX-512 opmask' INFO kernel: [ 0.000000] x86/fpu: Supporting XSAVE feature 0x040: 'AVX-512 Hi256' INFO kernel: [ 0.000000] x86/fpu: Supporting XSAVE feature 0x080: 'AVX-512 ZMM_Hi256' INFO kernel: [ 0.000000] x86/fpu: Supporting XSAVE feature 0x200: 'Protection Keys User registers' INFO kernel: [ 0.000000] x86/fpu: xstate_offset[2]: 576, xstate_sizes[2]: 256 INFO kernel: [ 0.000000] x86/fpu: xstate_offset[5]: 832, xstate_sizes[5]: 64 INFO kernel: [ 0.000000] x86/fpu: xstate_offset[6]: 896, xstate_sizes[6]: 512 INFO kernel: [ 0.000000] x86/fpu: xstate_offset[7]: 1408, xstate_sizes[7]: 1024 INFO kernel: [ 0.000000] x86/fpu: xstate_offset[9]: 2432, xstate_sizes[9]: 8 INFO kernel: [ 0.000000] x86/fpu: Enabled xstate features 0x2e7, context size is 2440 bytes, using 'compacted' format.