Messages in this thread | | | Date | Fri, 20 May 2022 10:52:40 -0700 | Subject | Re: [PATCHv2 2/3] x86/tdx: Clarify RIP adjustments in #VE handler | From | Dave Hansen <> |
| |
On 5/19/22 20:13, Kirill A. Shutemov wrote: > + /* > + * If the #VE happened due to instruction execution, GET_VEINFO > + * provides info on the instruction in out.r10. > + * > + * For #VE due to EPT violation, info in out.r10 is not usable and > + * kernel has to decode instruction manually to find out its length. > + */ > + if (ve->exit_reason != EXIT_REASON_EPT_VIOLATION) { > + ve->instr_len = lower_32_bits(out.r10); > + ve->instr_info = upper_32_bits(out.r10); > + } else { > + ve->instr_len = 0; > + ve->instr_info = 0; > + } > }
This is _better_, but I still don't like it. It still hides the magic down in here and if someone screws it up, they'll silently get a loop of #VE's. If we stick the logic a helper like:
int ve_instr_len(struct ve_info *ve) { if (WARN_ON_ONCE(ve->exit_reason != EXIT_REASON_EPT_VIOLATION)) return 0;
return ve->instr_len; }
and then folks consume the instruction length with that, we get a splat right where and when it goes wrong.
BTW, how do we know that all non-EPT_VIOLATION exits reasons are instruction execution?
| |