Messages in this thread | | | Date | Fri, 14 May 2021 12:38:27 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v2 2/4] mm: x86: Invoke hypercall when page encryption status is changed |
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On Fri, May 14, 2021 at 10:05:19AM +0000, Ashish Kalra wrote: > No, actually notify_addr_enc_status_changed() is called whenever a range > of memory is marked as encrypted or decrypted, so it has nothing to do > with migration as such. > > This is basically modifying the encryption attributes on the page tables > and correspondingly also making the hypercall to inform the hypervisor about > page status encryption changes. The hypervisor will use this information > during an ongoing or future migration, so this information is maintained > even though migration might never be initiated here.
Doh, ofcourse. This doesn't make it easier.
> The error value cannot be propogated up the callchain directly > here,
Yeah, my thinking was way wrong here - sorry about that.
> but one possibility is to leverage the hypercall and use Sean's > proposed hypercall interface to notify the host/hypervisor to block/stop > any future/ongoing migration. > > Or as from Paolo's response, writing 0 to MIGRATION_CONTROL MSR seems > more ideal.
Ok.
So to sum up: notify_addr_enc_status_changed() should warn but not because of migration but because regardless, we should tell the users when page enc attributes updating fails as that is potentially hinting at a bigger problem so we better make sufficient noise here.
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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