Re: [PATCH v3 1/2][4.15] VMX: delay p2m insertion of APIC access page

[Ian Jackson <iwj@xenproject.org>]

Jan Beulich writes ("Re: [PATCH v3 1/2][4.15] VMX: delay p2m insertion of APIC access page"):
> On 22.02.2021 12:25, Ian Jackson wrote:
> > Jan Beulich writes ("[PATCH v3 1/2][4.15] VMX: delay p2m insertion of APIC access page"):
> >> Inserting the mapping at domain creation time leads to a memory leak
> >> when the creation fails later on and the domain uses separate CPU and
> >> IOMMU page tables - the latter requires intermediate page tables to be
> >> allocated, but there's no freeing of them at present in this case. Since
> >> we don't need the p2m insertion to happen this early, avoid the problem
> >> altogether by deferring it until the last possible point.
> > 
> > Thanks.
> > 
> >>   This comes at
> >> the price of not being able to handle an error other than by crashing
> >> the domain.
> > 
> > How worried should I be about this ?
> 
> Not overly much I would say. The difference is between a failure
> (-ENOMEM) during domain creation vs the domain getting crashed
> before it gets first scheduled. This is certainly less friendly
> to the user, but lack of memory shouldn't typically happen when
> creating domains. Plus the memory talked about here is such that
> gets provided explicitly to the domain (the p2m pool), rather
> than a system wide pool.

OK, thanks.

Release-Acked-by: Ian Jackson <iwj@xenproject.org>