Messages in this thread | | | Date | Tue, 26 Apr 2022 14:34:53 +0200 | Subject | Re: [PATCH v2 0/2] Dirtying, failing memop: don't indicate suppression | From | Janosch Frank <> |
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[...] >>> >>> The only question is, do we need to change the suppression parameter in >>> access_guest_with_key >>> >>> (mode != GACC_STORE) || (idx == 0) >>> >>> to also check for prot != PROT_TYPE_KEYC >>> ? I think we do not need this as we have checked other reasons before. > > Yes, it is not necessary, the control flow is such that a protection exception > implies that is due to keys. >> >> To me this measure looks like a last resort option and the POP doesn't state a 100% what is to be done. Some instructions can mandate suppression instead of termination according to the architects. >> >> My intuition tells me that if we are in a situation where this would happen then we would be much better off just doing it by hand (i.e. in the instruction emulation code) and not letting this function decide. > > For the instructions we currently need to emulate in KVM we should be fine. > So the question is what's best for the future and for instructions emulated by user space. > Upward in the call stack (including user space), we don't know the failing address, > which complicates handling it in the emulation code. > You could chop up the memop in page chunks to find out, but that might have other issues. > > Since this behavior is very implicit and easy to overlook maybe we should document it > in the description of the memop ioctl?
Yeah, properly documenting this is the least we can do.
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