Re: [PATCH v2 2/4] mm: x86: Invoke hypercall when page encryption status is changed

[Paolo Bonzini]

On 19/05/21 14:06, Ashish Kalra wrote:
> Now these buffers have very short life and only used for immediate I/O
> and then freed, so they may not be of major concern for SEV
> migration ?

Well, they are a concern because they do break migration.  But it may be 
indeed good enough to just have a WARN ("bad things may happen and you 
get to keep both pieces") and not disable future migration.

A BUG must always be avoided unless you're sure that something *worse* 
will happen in the future, e.g. a BUG is acceptable if you have detected 
a use-after-free or a dangling pointer.  This is not the case.

Paolo

> So disabling migration for failure of address lookup or mapping failures
> on such pages will really be an overkill.
> Might be in favor of Steve's thoughts above of doing a BUG() here
> instead.