Re: [RFC 1/4] HVM x86 deprivileged mode: Page allocation helper

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 06/08/15 17:45, Ben Catterall wrote:
> This allocation function is used by the deprivileged mode initialisation code
> to allocate pages for the new page table mappings and page frames on the HAP
> page heap.
>
> Signed-off-by: Ben Catterall <Ben.Catterall@citrix.com>

This is fine for your test box, but isn't fine for systems out there
without hardware EPT/NPT support.  For older systems like that (or in
certain specific workloads), shadow paging is used instead.

This feature is applicable to any HVM domain, which means that it
shouldn't depend on HAP or shadow paging.

How much memory is allocated for the depriv area, and what exactly is
allocated in total?

I expect it isn't very much, and would suggest using
d->arch.paging.alloc_page() instead (which is the generic "get me some
memory accounted against the domain" helper) which looks as if it should
suffice.

Depending on exactly how much memory is needed, you might need to bump
the default minimum shadow pool size.

~Andrew