Re: [PATCH 3/3] x86/xen: allow nesting of same lazy mode

[Boris Ostrovsky]

On 9/13/23 7:38 AM, Juergen Gross wrote:
> When running as a paravirtualized guest under Xen, Linux is using
> "lazy mode" for issuing hypercalls which don't need to take immediate
> effect in order to improve performance (examples are e.g. multiple
> PTE changes).
>
> There are two different lazy modes defined: MMU and CPU lazy mode.
> Today it is not possible to nest multiple lazy mode sections, even if
> they are of the same kind. A recent change in memory management added
> nesting of MMU lazy mode sections, resulting in a regression when
> running as Xen PV guest.
>
> Technically there is no reason why nesting of multiple sections of the
> same kind of lazy mode shouldn't be allowed. So add support for that
> for fixing the regression.
>
> Fixes: bcc6cc832573 ("mm: add default definition of set_ptes()")
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>

For patches 2 and 3

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>