9 Nov
2021
9 Nov
'21
2:14 p.m.
On Tue, Nov 9, 2021 at 8:43 AM Brian Geffon bgeffon@google.com wrote:
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;
Sorry, I should have probably also shared the value of xfeatures at this point is 0x3: which appears to be: (X86_FEATURE_FPU | X86_FEATURE_XMM)
Brian